This is a classical error from the nginx webserver which is used on default hostware environments.
Cause
The cause of this error depends on the action which is being executed:
When a PDF gets generated in the administration, the PDF propably has lots of entries. In that case, the PDF generator needs more execution time than allowed by nginx.
Adjust configuration
To fix this issue, adjust the configuration of your nginx and php config.
nano /etc/php/8.3/fpm/php.ini
Press CTRL + W and search for "max_execution_time" in the file. Press enter to find that line.
The default value is 30 seconds. Adjust as needed, for example to 180 for 3 minutes.
