How to fix “Authentication failed because NTLM authentication has been disabled. [ERROR_NTLM_BLOCKED (0x791)]” – Error Code 1937


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Error Code 1937

Error code Error Code 1937 is a common Windows issue that typically arises from “Authentication failed because NTLM authentication has been disabled. [ERROR_NTLM_BLOCKED (0x791)]”.

Overview

In this article, we’ll focus on resolving the issue described as: “Authentication failed because NTLM authentication has been disabled. [ERROR_NTLM_BLOCKED (0x791)]”. This error, identified by the error code Error Code 1937, can impede your system’s performance, and here’s how you can fix it.

Identifying the Problem

Error Code 1937 is associated with a failure in NTLM authentication, a protocol used for authenticating users on a network. It often occurs when NTLM authentication has been disabled or is encountering issues. The error can manifest in various scenarios, such as when connecting to shared network resources, accessing websites, or while software installations.

Common Fixes

1. Enable NTLM Authentication

  • Navigate to “Control Panel\System and Security\Security Center”.
  • Click on “Change advanced security settings” in the left pane.
  • Select “Network security: LAN Manager authentication level”.
  • Set the level to “Send NTLMv2 response only” or “Send NTLMv2 response only. Refuse LM & NTLM”.

2. Clear NTLM Credentials Cache

  • Press “Windows Key + R” to open the Run dialogue.
  • Type “cmd” and click “OK”.
  • Enter the following command: cmdkey /list
  • Identify any credentials related to the affected network or service.
  • Enter the command: cmdkey /delete:<credential_name> to remove the credentials.

3. Disable Windows Defender Firewall

  • Open “Control Panel\System and Security\Windows Defender Firewall”.
  • Click on “Turn Windows Defender Firewall on or off” in the left pane.
  • Select “Turn off Windows Defender Firewall (not recommended)” for both private and public networks.

4. Check for Antivirus Interferences

  • Disable your third-party antivirus software temporarily.
  • If the issue persists, consider uninstalling the antivirus software.
  • After resolving the issue, reinstall the antivirus software and configure it to allow NTLM authentication.

Advanced Troubleshooting

1. Reset Winsock

  • Open “Command Prompt” as administrator.
  • Enter the following command: netsh winsock reset
  • Restart your computer.

2. Edit the Registry

  • Warning: Registry editing can have serious consequences. Back up your registry before proceeding.
  • Press “Windows Key + R” and type “regedit”.
  • Navigate to: \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
  • Right-click on the registry key and select “New” > “DWORD (32-bit) Value”.
  • Name the value “LmCompatibilityLevel” and set its value to “1”.
  • Restart your computer.

Conclusion

By implementing these fixes, you can effectively resolve Error Code 1937 and restore NTLM authentication on your system. Remember to keep your operating system and software up to date to minimize the risk of encountering this error in the future. If the problem persists despite trying all the solutions, consider seeking professional technical support to diagnose and resolve the underlying cause.