Plesk comes with a trial license key, which is already installed in the system. This license key provides limited functionality and is active only for a short period of time. Therefore, after installing Plesk, you should obtain a proper license key from Plesk or its partners and install it.
Plesk License Keys
You can install a Plesk license key either by entering an activation code or by uploading a license key file to Plesk. Learn how to do this in the section Installing a Plesk License Key.
Plesk license keys have a built-in expiration date. This has been implemented to help prevent fraud and theft. It requires the Plesk software to check with the Plesk licensing server within a 10-day period before the expiration date to verify that the key has not been reported stolen and is being used in accordance with the End User License Agreement (that is, installed on only one server). Once this is verified, the expiration date is extended. The verification runs automatically and you do not need to do anything unless there is a problem. If the key has expired, go to Tools & Settings > License Management and click Retrieve Keys. If the key cannot be updated, contact your reseller, or Plesk (if you purchased the license key directly from Plesk).
Note: Plesk uses the TCP port 5224 for connections to the licensing server. Please make sure that the port is not blocked by a firewall. To test the connection to the licensing server at anytime, click Retrieve Keys in Tools & Settings > License Management.
Additional License Keys
Additional license keys are used to activate third-party software in Plesk. Typically, these components are commercial Plesk extensions such as anti-virus software, webmail software, and so on. Additional keys are associated with the Plesk license key and can be found in Tools & Settings > License Management > Additional License Keys. Learn how to order add-ons and install additional license keys in the section Installing Additional License Keys for Plesk Add-ons.