Flush DNS and Switch Servers: Open Command Prompt as Administrator
👇 See all 2 solutions belowWhat is Error 4400?
Windows System Error Code 4400, known as ERROR_APP_DATA_NOT_FOUND, is a DNS & WINS error that occurs during DNS resolution and WINS name resolution. The error indicates that: Fast Cache data not found. When this error is encountered, the Windows operating system was unable to complete the requested operation within the DNS/WINS services subsystem. The error code 4400 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_APP_DATA_NOT_FOUND 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 DNS resolution and WINS name resolution is essential for effective troubleshooting.
Common Causes
- System resource conflict: Fast Cache data not found.
- DNS server misconfigured
- Stale DNS cache entries
- Hostname cannot be resolved
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Read the full guide →Step-by-Step Solutions
- Open Command Prompt as Administrator
- Run: ipconfig /flushdns
- Change DNS to Google (8.8.8.8) or Cloudflare (1.1.1.1)
- Run: ipconfig /registerdns
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 "*4400*" -or $_.Message -like "*ERROR_APP_DATA_NOT_FOUND*"} | Format-List💡 Open PowerShell as Administrator, paste the command above, and press Enter.
Prevention Tips
- Use reliable DNS (8.8.8.8 or 1.1.1.1)
- Flush DNS cache periodically
- Monitor DNS resolution performance