When opening Plesk the following message appears:
PLESK_ERROR: Error: The license key is invalid. In order to use Plesk, you need to obtain and install a new valid license key.
Your license key has expired. To continue using your Plesk, you must purchase a non-expiring commercial license key.
During the attempt to retrieve license key or install a valid one through Plesk > License Management, the following error appears:
PLESK_ERROR: Error: Updated license key is not valid.
The following command shows incorrect date:
Wrong time is set on the server.
Set the correct time with a help of commands described here: How to Change the Linux Date and Time: Simple Commands