Reset Internet Settings: Open Command Prompt as Administrator
👇 See all 2 solutions belowWhat is Error 15400?
Windows System Error Code 15400, known as ERROR_CANNOT_SWITCH_RUNLEVEL, is a Internet & WinHTTP error that occurs during WinHTTP, WinInet, and internet protocols. The error indicates that: The requested run level switch cannot be completed successfully. When this error is encountered, the Windows operating system was unable to complete the requested operation within the internet services subsystem. The error code 15400 is returned by the GetLastError() function and provides developers with a specific identifier to diagnose the root cause of the failure. The symbolic name ERROR_CANNOT_SWITCH_RUNLEVEL maps directly to this numeric code and is commonly referenced in Microsoft documentation, developer forums, and system logs. Understanding this error and its context within WinHTTP, WinInet, and internet protocols is essential for effective troubleshooting.
Common Causes
- System resource conflict: The requested run level switch cannot be completed successfully.
- Proxy misconfigured
- SSL/TLS handshake failure
- Client certificate expired
Troubleshooting COM and DCOM Architectural Failures (Event ID 10016)
A comprehensive guide on Component Object Model (COM), Distributed COM (DCOM), and how to safely interpret and resolve Event ID 10016 errors.
Read the full guide →Step-by-Step Solutions
- Open Command Prompt as Administrator
- Run: netsh winhttp reset proxy
- Open Internet Options → Advanced → Reset
- Restart your browser and applications
Video Tutorials
Diagnostic Command
Run this PowerShell command to find related events in your system log:
Get-EventLog -LogName System -Newest 20 | Where-Object {$_.Message -like "*15400*" -or $_.Message -like "*ERROR_CANNOT_SWITCH_RUNLEVEL*"} | Format-List💡 Open PowerShell as Administrator, paste the command above, and press Enter.
Prevention Tips
- Use centralized proxy management
- Keep root certificates updated
- Disable legacy SSL 3.0 protocol