The following error appears when accessing Plesk:
The license key is invalid. In order to use Plesk, please obtain and install a new valid license key.
The amount of currently used resources overrides the limits defined by your license.
The number of websites hosted on the server exceeds the limits defined by your license. You have XXX sites hosted; your license allows hosting only 30 (10) sites.
License has been updated recently. For example, Web Host type of license with unlimited number of domains has been changed to Web Admin (10 domains only) or Web Pro (30 domains only).
Web Host license used previously had unlimited number of domains. Once new license exceeds the domain limit (10 domain for Web Admin or 30 domains for Web Pro), these domains become invisible in Plesk interface and it is not possible to manage them there.
To resolve the issue, the license can be upgraded to the type which covers required number of domains. For example, if you have only up to 30 domains, you can change license from Web Admin (10 domains) to Web Pro (30 domains). Alternatively, it is possible reduce the number of domains to the allowed limit:
Using Plesk GUI
Using the command line