The server is temporarily unable to service your request due to maintenance down

If the PHP-FPM pool configuration file for the user is missing, the PHP-FPM service cannot manage requests for that user, resulting in the errors you're encountering. To resolve this, you'll need to recreate the missing configuration file.Locate Default Pool ConfigurationCheck if there’s a default template or example configuration file:
 Recreate the Pool ConfigurationIf no template exists, create the file manually: