How to Fix Windows ERROR_81: Step-by-Step Troubleshooting Guide

Windows ERROR_81 can be frustrating. It typically indicates a network connectivity issue, often related to problems with VPN access or domain authentication. If you’re encountering this error, don’t worry — this comprehensive guide will walk you through the troubleshooting process, step by step.

What is Windows ERROR_81?

Before diving into the fix, understanding the error helps. ERROR_81 usually manifests as:

• “ERROR 81: The remote access connections are busy or unavailable.”
• Issues connecting to a VPN or domain.
• Network-related failures when accessing shared resources.

This error points to a problem with network connectivity, permissions, or misconfigured settings.

Why Does ERROR_81 Appear?

Common causes include:

• Network adapters misconfiguration.
• VPN connection conflicts.
• Firewall or antivirus software blocking access.
• Incorrect DNS or routing settings.
• Interrupted or busy remote access server.

How to Fix Windows ERROR_81: Step-by-Step

Step 1: Restart Your Computer and Network Devices

It sounds simple, but many network problems resolve after a restart.

• Restart your PC: This refreshes system services.
• Restart your modem/router: Unplug for 30 seconds, then plug back in.
• Restart VPN client and try connecting again.

Step 2: Check Your Network Connection

Make sure your PC is connected to the internet without issues:

• Click the network icon on your taskbar.
• Open Network & Internet settings.
• Run Network Troubleshooter to detect and fix potential problems.
• Ensure you’re not connected to a restricted or public Wi-Fi that blocks VPN.

Step 3: Disable Conflicting VPN or Network Software

If you use multiple VPNs or network utilities, conflicts can cause ERROR_81.

• Open Control Panel > Programs and Features.
• Temporarily uninstall or disable secondary VPN clients.
• Make sure only the VPN you intend to use is active.
• Also, briefly disable third-party firewall/antivirus for testing.

Step 4: Reset Network Settings

Resetting network configurations can clear corrupt settings:

1. Open Command Prompt as Administrator:

   • Press Windows + S, type cmd, right-click Command Prompt, select “Run as administrator.”

2. Execute these commands one by one:

   netsh winsock reset
   netsh int ip reset
   ipconfig /release
   ipconfig /renew
   ipconfig /flushdns

3. Restart your PC after running these commands.

Step 5: Verify VPN Configuration

If you’re connecting via VPN, errors might stem from incorrect settings:

• Check VPN server address and your credentials.
• Ensure VPN protocols (PPTP, L2TP, SSTP…) are correctly set.
• Refer to your VPN provider or IT team for correct settings.
• If possible, try connecting from a different device/network.

Step 6: Check Windows Firewall and Security Settings

Firewalls often block remote access ports needed by VPN.

• Open Windows Defender Firewall.
• Click Allow an app or feature through Windows Defender Firewall.
• Ensure your VPN app is allowed on both Private and Public networks.
• Temporarily disable Windows Firewall and test the connection. If it fixes the issue, adjust firewall rules properly.

Step 7: Update Network Adapter Drivers

Outdated drivers cause compatibility problems:

• Press Windows + X, select Device Manager.
• Expand Network adapters.
• Right-click your adapter, select Update driver.
• Choose Search automatically for updated driver software.
• Restart your PC after updating.

Step 8: Review Domain or Workgroup Settings (If Applicable)

For domain-joined PCs, ERROR_81 could indicate domain trust issues.

• Ensure your PC is connected to the corporate network.
• Confirm your domain account credentials are valid.
• Contact your domain administrator for help if you can’t authenticate.

Additional Tips

• Test with another network: Try a mobile hotspot or different internet.
• Use built-in Windows VPN: If your third-party VPN fails consistently.
• Review Event Viewer logs: For detailed error messages. Press Windows + X > Event Viewer > Windows Logs > System/Application.

Conclusion

Windows ERROR_81 can feel like a big hurdle, but with these methodical steps, you’ll most likely find the culprit and fix it. Network errors are often caused by misconfigurations or conflicts — so checking connection status, resetting network settings, and verifying VPN/firewall settings are key.

Need More Help?

If you continue facing ERROR_81 after these steps:

• Contact your VPN service support.
• Reach out to your corporate IT department.
• Visit Microsoft’s support forums for similar cases.

Hopefully, this guide helped get you back online smoothly! Stay patient, follow each step, and you’ll beat ERROR_81 soon.