A customer with Plesk in VPS subscription cannot add a domain to Plesk from POA Customer Control Panel, the domain stays in the "failed to add" status on the domain management section of CCP.
There are no failed tasks in POA Task Manager related to the failed domain or customer subscription in question. In POA debug log you can find the following error message related to the problem domain adding:
There are no IPs in Plesk client's pool
If there is no such message, please also check the completed task "Plesk in VPS *: register domain". Its output can contain the same message.
All IP addresses in Plesk are marked as dedicated, POA cannot find free IP address to add to the client's (owner of the domain being added) IP pool and fails to create a domain.
Change the type of the IP address which is listed in the 'VPS Management' section in POA Customer Control Panel to 'Shared' in Plesk and resubmit the domain to Plesk in POA CCP.