The server received an invalid response from an upstream process.
WHAT IT MEANS
Something between the web server and your application failed. The application did not respond correctly, or did not respond at all.
COMMON CAUSES
The PHP process crashed or was terminated Memory exhausted, causing the process to be killed A script exceeding execution time A temporary server condition Excessive concurrent requests
WHAT TO CHECK
cPanel > Metrics > Errors for entries around the time cPanel > Resource Usage for whether you hit a limit Whether it is constant or intermittent
IF IT IS INTERMITTENT
Usually resource pressure at peak times. Check Resource Usage for spikes matching the errors.
Caching is the usual fix.
IF IT IS CONSTANT
Something is failing every time. Check the error log for a PHP fatal error or a memory message.
Disable recently added plugins and retest.
IF IT APPEARED SUDDENLY WITH NO CHANGE FROM YOU
Check Client Area > Network Issues. A server-side condition produces this.
WHAT TO SEND US
The time, whether it is constant or intermittent, and your Resource Usage graph for that period.
