WHMCS version 4.41 has split the Plesk server automation module out into three separate versions; plesk8, plesk9 and plesk10, but the upgrade script doesn’t handle changing the automation module settings for either your servers or your products/services.
As a result of this short sightedness on the developer’s part you will loose all automation of your Plesk servers (account creation, suspension, termination, statistics updates etc.) and start experiencing fatal PHP errors in both the admin and client areas of WHMCS where the functions provided by the old “plesk” module are used (which is basically any area using products/services or servers defined with the “plesk” module) unless you retain the generic “plesk” module from your previous WHMCS 4.31 install.
As copying over the “modules/servers/plesk” folder from WHMCS v4.31 or symlinking the appropriate folder of one of the new modules to “modules/servers/plesk” seems like a massive dirty hack to me, instead I decided to do what the WHMCS 4.41 installer should have done in the first place and fix the database to use the correct version of the new Plesk server module.
For me the new “plesk9” module is the one to use, but you can adjust the following SQL appropriately to suit your needs (remember to backup your database however you see fit before you begin!):
UPDATE tblproducts SET servertype=’plesk9′ WHERE servertype=’plesk’;
UPDATE tblservers SET type=’plesk9′ WHERE type=’plesk’;
As usual with WHMCS, there are no mention of any changes to the Plesk module in the release notes for version 4.41.