A Plesk license could not be found via the
License Manager in Parallels Business Automation - Standard (PBA-S) Provider's Panel (PCC) or Reseller's Panel (RCC):
Top > Service Director > License Manager > Licenses
It can only be seen from
Top > Account Director > Subscription Manager > Subscriptions > %subscription% > Billable Items
Also it's active in KA.
The license key is assigned to a missing KA plug-in.
Since the issue requires complex manipulations with the database, it is recommended to contact Parallels Technical Support for assistance.