The license key is invalid -Plesk Error. 
Error: The license key is invalid. In order to use the Panel, you need to obtain and install a new valid license key. The amount of currently used resources overrides the limits defined by your license.
Cause of the error---------
Corrupted registry.xml
Resolution---------
Connect to the server via RDP and remove or move the damaged file. It can be found in one of the following folders, depending on the OS used:
Linux:
/etc/sw/keys/
Windows:
%plesk_dir%\admin\repository\
After the file is removed, login to Plesk. The registry.xml file will be automatically recreated.
