After you install Plesk, a trial license key for 14 days is installed by default. To continue using Plesk after the trial license key expires, you should obtain a lease license key or purchase a permanent license key.
A leased license implies that you pay for a limited time during which you can use Plesk, say, for a couple of months. During the lease period, Plesk will perform free monthly updates of your license key. The lease license includes free upgrades to all new major versions of Plesk.
The permanent license implies that you buy a Plesk license for a lifetime. A permanent license is updated every three months for free. Upgrading a Plesk installation with a permanent license to the next major version requires a separate payment unless you use Software Update Service (SUS). See https://kb.plesk.com/en/111 for more information on SUS.
Plesk license keys have a grace period of 10 days right before the expiration date. During the grace period, Plesk automatically performs daily attempts to update the license key automatically. If an automatic update fails, Plesk notifies the administrator. If you do not update a license key during the grace period, it expires and blocks Plesk functions until you install a valid license key.
Plesk defines whether it needs to update the license key using the
update-keys.php utility located in the
%plesk_dir%admin\plib\DailyMaintainance\ directory, where
%plesk_dir% is an environment variable denoting the Plesk installation
directory. This utility checks the license grace period and expiration
date and tries to retrieve a new license key or blocks Plesk.
Plesk runs the utility every day as a part of the daily maintenance
script. If you want to check for license updates, you can run the script
manually by executing the command
%plesk_bin%\php.exe" -d auto_prepend_file="%plesk_dir%admin\plib\DailyMaintainance\script.php".
You can retrieve and manage license keys through the Plesk GUI. The information about current license key and controls for managing license keys are located in Server Administration Panel > Tools & Settings > License Management.