Symptoms
A Sales Order in PBA is stuck in the Provisioning status, an Order Item for creating new POA subscription is stuck.
The subscription was actually created and enabled in POA, all tasks related to the subscription provisioning in POA are successfully processed.
There is no 'Post event to PBA' task in POA which should notify PBA that subscription provisioning completed in POA.
Cause
The customer account in question has ID less than 1000000. POA does not treat accounts with ID < 1000000 as PBA accounts, so POA does not send notification about successful subscription creation to PBA.
Resolution
Contact the Parallels Support Team to resolve the problem.