PHP did not respond properly to the request. As a result, Apache considers the PHP-FPM service to be unavailable.
I get this when trying to activate the plugin.
Let me know if you need the log.
For specific information about the error, see the Apache error log at:
The root cause of this error is often slow PHP code. You should disable any plugins the app is using and check the app's PHP error log and PHP slow request log located at: