503 Temporarily Unavailable for a website on a recently activated or enabled Subscription

Symptoms

• A website that was enabled or activated recently still shows a 503 Temporary Unavailable error
• The domain is listed as Active in the Plesk GUI
• When attempting to change the PHP version by going to Plesk > Domains > example.com > PHP Settings, the following warningis shown:
  

  PLESK_ERROR: You have changed the PHP handler settings. If you save these changes, PHP scripts on your website may stop for 999999 seconds because of your server configuration.
  Below are the details on the website's PHP configuration. You can change the PHP configuration if the hosting provider grants you the corresponding permission.

• The Apache restart interval in Plesk > Tools & Settings > General Settings > Apache Web Server is set to a very high value (999999, 100000, etc.)

Cause

Apache needs to get restarted in order to apply the necessary change to the status of the subscription. When the restart interval is set to a very high value, it may take days or weeks for this restart to occur, due to which the change in status for the subscription is delayed for that time.

Resolution

If Apache graceful restart is enabled on the server, it is recommended tokeep the Apache restart interval value at 0.
If setting the Apache restart interval to a certain value, it should generally not be set to a value above 3600 seconds (one hour), because this may result in long delays before changes to web server configuration which require a restart are applied.