How to Fix RDP Authentication Error Has Occurred (CredSSP & NLA Guide)

RDP Authentication Error Has Occurred on Windows VPS

The message “An authentication error has occurred” appears immediately after the connection attempt begins, before credentials are validated and before a desktop session is created.

In the RDP connection flow, TCP establishes the transport channel first. Once that succeeds, the client and server move to security negotiation, where encryption protocol, CredSSP handshake, and Network Level Authentication are agreed upon. If this negotiation fails, Windows terminates the attempt and displays what administrators recognize as the rdp authentication error has occurred message.

At this point, the password has not been evaluated. The interruption happens inside the authentication protocol layer.

What Does This Authentication Error Mean in Remote Desktop?

When the system shows an an authentication error has occurred rdp message, the client and server were unable to align on the security parameters required to proceed.

The failure usually involves encryption level selection, CredSSP compatibility, NLA enforcement, or policy-based restrictions that affect credential delegation. It is a remote desktop authentication error, but not a credential rejection, because the login data has not yet been submitted for verification. The session is blocked during negotiation, not during account validation. In practice, most incidents stem from either protocol mismatch or policy enforcement that prevents the security layer from completing.

Common Causes

CredSSP Mismatch

CredSSP handles secure credential delegation during the pre-session exchange. After Microsoft introduced the credssp encryption oracle remediation update, systems with inconsistent patch levels began refusing each other’s connections even though basic network connectivity remained intact.

This produces situations described as credssp windows server mismatch, rdp credssp update issue, or credssp patch mismatch client server. The negotiation fails before any credential data is processed, which is why no failed login events appear in the security logs. In environments where one endpoint is fully updated and the other is not, the newer system enforces stricter validation and rejects the session during the security handshake rather than during authentication itself.

NLA Issues

Network Level Authentication RDP requires authentication to occur before a remote session is established. Because it relies on CredSSP and compatible encryption support, any incompatibility between client and server security layers can interrupt the exchange.

If the server enforces NLA and the client cannot negotiate the expected encryption level, the attempt is stopped with an nla rdp error or what appears as an rdp encryption level mismatch. The system is not rejecting a password; it is rejecting the negotiated security context. Temporarily disabling NLA can confirm whether the interruption occurs inside the pre-session authentication phase. However, this should remain a diagnostic measure rather than a permanent configuration change.

Outdated Updates

Patch misalignment is a frequent trigger of the rdp authentication error has occurred condition.

A system missing recent security updates may not support the encryption requirements expected by the opposite endpoint. Conversely, a fully updated client may enforce protocol behavior that an older server cannot satisfy. In both cases, the connection stops before credential validation begins.

Administrators often notice the issue after maintenance cycles, describing it as an rdp error after windows update or a windows security patch rdp issue. In some situations, updating CredSSP on Windows Server resolves the mismatch immediately. Maintaining consistent update levels across endpoints reduces these negotiation failures significantly.

Group Policy Restrictions

Security negotiation may also fail because of policy enforcement, especially in domain-controlled environments where central configuration overrides local settings.

In gpedit.msc, under Computer Configuration → Administrative Templates → System → Credentials Delegation, several options directly affect how credentials are handled. Settings such as Allow delegating fresh credentials, Encryption Oracle Remediation, and the configured Remote Desktop security layer can prevent the handshake from completing if the policy expectations do not match client capabilities.

A restrictive group policy rdp authentication configuration may therefore block the session before authentication logic is reached. Because the interruption occurs at protocol level, the absence of login events can mislead troubleshooting efforts.

How to Fix It

Begin by confirming update alignment on both client and server systems. Install pending Windows security updates, reboot both endpoints, and test the connection again. A large portion of credssp authentication error cases resolve once patch levels are synchronized.

If the problem continues, open gpedit.msc and review the Credentials Delegation settings. Temporarily adjusting the Encryption Oracle Remediation policy can help determine whether CredSSP compatibility is the root cause. If the connection succeeds under relaxed policy, restore secure settings after updating the outdated endpoint.

For cases involving NLA enforcement, temporarily disable NLA on the server and attempt reconnection. If the session establishes successfully, investigate client compatibility rather than leaving NLA disabled.

When troubleshooting environments deployed on a Windows VPS server, ensure that the system template is fully updated and that no inherited security policies restrict credential delegation. Inconsistent base images or delayed update cycles can surface as authentication-layer failures even when network connectivity remains stable.

Event Viewer provides confirmation of protocol-level interruptions. Under Applications and Services Logs → Microsoft → Windows → TerminalServices, look for errors indicating handshake or security negotiation failure rather than login rejection.

Avoid shifting analysis toward firewall configuration or port testing at this stage, as those generate different error patterns tied to transport or service availability rather than authentication protocol exchange.

Step-by-Step Actions to Fix the Error

If the rdp authentication error has occurred message appears, follow these practical steps to identify and resolve the issue. These checks target the most common causes related to CredSSP compatibility, NLA configuration, and security policy mismatches.

1. Install Windows Updates on Both Systems

Update alignment between the RDP client and server is the most common solution.

On the Windows VPS or server:

1. Open Settings

2. Go to Windows Update

3. Click Check for updates

4. Install all available security updates

5. Restart the system

Repeat the same process on the client computer used for the Remote Desktop connection.

Once both endpoints are updated, attempt the RDP connection again.

2. Adjust the CredSSP Policy if Systems Cannot Be Updated Immediately

If one endpoint cannot be updated right away, temporarily modifying the Encryption Oracle Remediation policy can allow the connection.

On the client computer:

1. Press Win + R

2. Run:

gpedit.msc

3. Navigate to:

Computer Configuration
→ Administrative Templates
→ System
→ Credentials Delegation

4. Open Encryption Oracle Remediation

5. Set the policy to:

Enabled
Protection Level: Vulnerable

6. Apply the change and reconnect through RDP.

This adjustment should only be used temporarily. After updating both systems, restore the policy to Not Configured or Mitigated.

3. Temporarily Disable Network Level Authentication

If the interruption is caused by an NLA negotiation issue, temporarily disabling NLA can confirm the cause.

On the Windows VPS server:

1. Open Server Manager

2. Go to Local Server

3. Click the Remote Desktop configuration option

4. Uncheck:

Allow connections only from computers running Remote Desktop with Network Level Authentication

5. Apply the changes and test the connection again.

Once the underlying issue is resolved, NLA should be enabled again for security.

4. Restart the Remote Desktop Service

In some situations the RDP service may require a restart after policy or update changes.

Run the following command on the server in PowerShell with administrative privileges:

Restart-Service TermService -Force

Alternatively:

net stop termservice
net start termservice

After restarting the service, reconnect using Remote Desktop.

5. Check Remote Desktop Logs in Event Viewer

If the issue persists, confirm that the interruption occurs during the security negotiation phase.

Open Event Viewer and navigate to:

Applications and Services Logs
→ Microsoft
→ Windows
→ TerminalServices

Look for events related to:

● CredSSP negotiation failure

● security handshake errors

● authentication protocol mismatch

These entries help confirm that the failure occurs before credential validation begins.

Quick Practical Checklist

If you encounter the rdp authentication error has occurred message:

● Install Windows updates on both client and server

● Verify CredSSP compatibility

● Review Credentials Delegation policy settings

● Temporarily disable NLA to test negotiation compatibility

● Restart the Remote Desktop service

● Check Event Viewer logs for protocol-level errors

Following these steps helps isolate the exact stage where the Remote Desktop authentication process fails and allows administrators to correct the underlying configuration mismatch.

How to Confirm It’s Not a Credential Issue

The rdp authentication error has occurred message appears before credentials are validated.

If the issue were account-related, the system would display feedback such as your credentials did not work rdp or report an account lockout. Network-level failures, on the other hand, generate messages like “the remote computer refused the connection,” indicating transport or service problems instead of negotiation breakdown.

When the error appears immediately without password feedback, the failure is occurring inside the security negotiation phase rather than during credential verification. If you are troubleshooting multiple Remote Desktop connection issues across systems, identifying the precise stage at which the process fails prevents unnecessary configuration changes. Errors that explicitly reference rejected credentials belong to a separate diagnostic path.

For a structured breakdown of those login-level failures, refer to the article titled Your Credentials Did Not Work. For a broader overview of Remote Desktop failure scenarios and how they relate to each connection stage, consult the complete RDP troubleshooting guide.

Quick Diagnostic Summary

If you encounter the rdp authentication error has occurred message:

● Verify update alignment on both endpoints

● Check CredSSP compatibility

● Review NLA enforcement

● Inspect Credentials Delegation policy

● Confirm in Event Viewer that the interruption occurs before credential validation

The failure originates in security negotiation, not in login processing. Keeping that distinction clear prevents unnecessary debugging and keeps analysis focused on the correct protocol layer.

Conclusion

The rdp authentication error has occurred message is not related to incorrect credentials or account problems. It indicates a failure during the security negotiation phase of the Remote Desktop connection process, before login verification even begins.

In most environments, the issue is caused by one of the following conditions:

● CredSSP compatibility mismatch between client and server

● Inconsistent Windows update levels

● Network Level Authentication negotiation failures

● Restrictive credential delegation policies

Because the interruption happens at the protocol level, troubleshooting should focus on security configuration alignment rather than passwords, firewall rules, or port availability.

Keeping Windows systems updated, maintaining consistent security policies, and verifying CredSSP compatibility across endpoints significantly reduces the likelihood of encountering this error.

When administrators understand that the failure occurs before credential validation, diagnosing Remote Desktop connection problems becomes far more precise and efficient.

FAQ

You ask, and we answer! Here are the most frequently asked questions!

Why does the “RDP authentication error has occurred” appear before I enter my password?
- This happens because the failure occurs during the security negotiation phase of the Remote Desktop connection process. Before credentials are validated, the client and server must agree on encryption protocols, CredSSP authentication, and Network Level Authentication requirements. If this negotiation fails, Windows terminates the connection attempt and displays the rdp authentication error has occurred message.
Can outdated Windows updates cause this RDP error?
- Yes. One of the most common reasons for this issue is a CredSSP update mismatch between the RDP client and the server. If one system has newer security patches while the other does not, the updated system may refuse the connection during the authentication handshake. Installing the latest Windows updates on both endpoints usually resolves the problem.
Is it safe to disable Network Level Authentication (NLA)?
- Disabling NLA can help confirm whether the problem is related to authentication negotiation. However, it should only be used as a temporary troubleshooting step. Network Level Authentication improves security by requiring authentication before the remote session is created. After diagnosing the issue, NLA should be enabled again.
Does this error mean my login credentials are incorrect?
- No. When credentials are incorrect, Windows typically displays messages such as “Your credentials did not work.” The rdp authentication error has occurred message appears earlier in the connection process and indicates a failure in the authentication protocol or security negotiation rather than a rejected password.
Can firewall or port issues cause this error?
- Usually not. Firewall or port problems normally produce different errors, such as connection timeouts or messages indicating that the remote computer refused the connection. The rdp authentication error has occurred message specifically indicates a problem during the authentication protocol exchange rather than a network transport issue.