WordPress website hosted on Plesk server is not available: The website is undergoing scheduled maintenance

Symptoms

• WordPress-based website hosted on a Plesk server shows the following message when accessing it in the web browser:

  The website is undergoing scheduled maintenance.
  Sorry for the inconvenience. Come back a bit later, we will be ready soon!

• On attempts to open website pages (even non-existent), there is the next error can be shown:

  503 Service Unavailable

Cause

WordPress maintenance mode is enabled for the website manually, or by the WordPress upgrade task.

Resolution

Disable maintenance mode for WordPress instance using WP Toolkit:

1. Log into Plesk;

2. Go to Domains > example.com > WordPress and switch off the checkbox Maintenance mode in the card of the affected instance: