Fix Microsoft Proxy Authentication Error Code 2606 On PC

Verify Credentials:

• Double-check username:
  • Carefully retype your username, paying attention to capitalization and any special characters.
  • If possible, copy and paste the username from a reliable source.
• Confirm password accuracy:
  • Ensure Caps Lock is off.
  • Double-check for typos.
  • If possible, try typing the password into a text editor to verify it's what you expect before entering it into the login field.
  • If you've forgotten your password, use the "Forgot Password" or "Reset Password" option provided by the login screen.
• Ensure domain is correct:
  • If you're logging into a domain network, make sure you're using the correct domain name. It's often in the format "domain\username" or "[email address removed]".
  • If you're unsure of the correct domain, contact your network administrator.

Restart Devices:

• Restart PC:
  • Click the Start button.
  • Select "Power" and then "Restart."
• Restart router/modem:
  • Unplug the power cables from your router and modem.
  • Wait for about 30 seconds.
  • Plug the modem back in and wait for it to fully power on (usually indicated by steady lights).
  • Plug the router back in and wait for it to fully power on.

Check Proxy Settings:

• Examine Internet Options (Windows):
  • Open the Control Panel.
  • Search for and select "Internet Options."
  • Go to the "Connections" tab.
  • Click "LAN settings."
• Review LAN settings:
  • Check if "Use a proxy server for your LAN" is selected. If you're not using a proxy, it should be unchecked.
• Disable proxy temporarily:
  • If "Use a proxy server for your LAN" is checked, uncheck it and click "OK."
  • Test your network connection.

Clear Browser Data:

• Clear browser cache (Chrome):
  • Open Chrome.
  • Click the three vertical dots (More) in the top right corner.
  • Go to "More tools" and then "Clear browsing data."
  • Select "Cached images and files" and "Cookies and other site data."
  • Choose a time range (e.g., "All time").
  • Click "Clear data."
• Delete cookies (Firefox):
  • Open Firefox.
  • Click the three horizontal lines (Menu) in the top right corner.
  • Go to "Settings" then "Privacy & Security".
  • In the "Cookies and Site Data" section, click "Clear Data...".
  • Select "Cookies and Site Data" and "Cached Web Content",¹ then click "Clear".
• Remove browsing history (Edge):
  • Open Edge.
  • Click the three horizontal dots (Settings and more) in the top right corner.
  • Go to "Settings" then "Privacy, search, and services".
  • Under "Clear browsing data" click "Choose what to clear".
  • Select "Browsing history", "Cookies and other site data", and "Cached images and files" then click "Clear now".

Network Troubleshooting:

• Run Network troubleshooter (Windows):
  • Open the Settings app (Windows key + I).
  • Go to "System" and then "Troubleshoot."
  • Click "Other troubleshooters."
  • Find "Internet Connections" or "Network Adapter" and click "Run."
  • Follow the on-screen instructions.
• Release/renew IP address (Windows):
  • Open Command Prompt as administrator (search for "cmd," right-click, and select "Run as administrator").
  • Type ipconfig /release and press Enter.
  • Type ipconfig /renew and press Enter.
  • Type exit and press Enter.²
• Flush DNS (Windows):
  • Open Command Prompt as administrator.
  • Type ipconfig /flushdns and press Enter.
  • Type exit and press enter.

Disable Conflicting Software:

• Temporarily disable antivirus:
  • Right-click the antivirus icon in the system tray.
  • Look for an option to disable or turn off protection.
  • Disable it temporarily for testing.
  • Remember to re-enable it after testing.
• Disable firewall:
  • Open the Control Panel.
  • Search for and select "Windows Defender Firewall" or "Windows Firewall."
  • Click "Turn Windows Defender Firewall on or off."
  • Select "Turn off Windows Defender Firewall" for both private and public network³ settings.
  • Remember to re-enable it after testing.
• Close VPN connections:
  • Disconnect from any active VPN connections.

Update/Reinstall Drivers:

• Update network drivers (Windows):
  • Open Device Manager (search for "Device Manager" in the Start menu).
  • Expand "Network adapters."
  • Right-click your network adapter and select "Update driver."
  • Select "Search automatically for drivers."
• Reinstall network drivers (Windows):
  • Open Device Manager.
  • Expand "Network adapters".
  • Right click your network adapter and select "Uninstall device".
  • Check the box to delete the driver software.
  • Restart your computer. Windows will generally reinstall the driver automatically. If not, open device manager, right click the computer name at the top of the list, and select "Scan for hardware changes".

System File Check:

• Run SFC scan (Windows):
  • Open Command Prompt as administrator.
  • Type sfc /scannow and press Enter.
  • Wait for the scan to complete.
• Run DISM tool (Windows):
  • Open Command Prompt as administrator.
  • Type DISM /Online /Cleanup-Image /RestoreHealth and press Enter.
  • Wait for the process to complete.⁴

Reset Internet Options:

• Reset Internet Explorer settings (Windows):
  • Open the Control Panel.
  • Search for and select "Internet Options".
  • Go to the "Advanced" tab.
  • Click "Reset".
  • Follow the on-screen instructions.

Registry Check:

• Verify proxy related registry keys (Windows):
  • Open Registry Editor (search for "regedit" and run as administrator).
  • Navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings.
  • Look for keys like ProxyEnable, ProxyServer, and ProxyOverride.
  • If you're not using a proxy, ProxyEnable should be set to 0.
  • Be very careful when editing the registry, as incorrect changes can cause system instability.
  • It is best to export the registry key before making changes.
• It is also useful to check HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings

Check Group Policy:

• Verify group policy proxy settings (Windows Pro/Enterprise):
  • Open Group Policy Editor (search for "gpedit.msc" and run as administrator).
  • Navigate to User Configuration > Windows Settings > Internet Explorer Maintenance > Connections > Proxy Settings
  • Or navigate to Computer Configuration > Administrative Templates > Windows Components > Internet Explorer > Internet Control Panel⁵ > Connections.
  • Verify the proxy settings are correct, or are not enabled if they should not be.

New User Profile:

• Create a new user account (Windows):
  • Open the Settings app.
  • Go to "Accounts" and then "Family & other users."
  • Click "Add someone else to this PC."
  • Follow the on-screen instructions.
  • Test the network connection in the new user account.

System Restore:

• Perform system restore (Windows):
  • Search for "Create a restore point" and open it.
  • Click "System Restore."
  • Follow the on-screen instructions to select a restore point from before the issue started.

Windows Update:

• Ensure Windows is up to date:
  • Open the Settings app.
  • Go to "Windows Update" and click "Check for updates."
  • Install any available updates.

Contact IT Support:

• Contact network administrator:
  • If you're on a corporate or managed network, contact your IT department for assistance.
• Contact Microsoft support: