Provider successfully scheduled migration of a VPS in the POA Provider Control Panel, no error or warning messages were shown.
Still, the VPS does not appear in the list of scheduled VPS migrations at Service Director > Virtuozzo Manager > Migration Tasks.
The status of the VPS in question is 'Has Problems'.
A VPS may have the 'Has Problems' status due to different reasons, e.g. some provisioning tasks for the VPS failed or the VPS Hardware Node experienced problem.
Usually it is enough to stop/unmount the VPS on the hardware node where it is located to solve the problem:
Log into the Hardware Node where the VPS is located
Stop the VPS:
vzctl stop VPS_ID
Replace VPS_ID with the actual ID of the VPS.
After that go into the POA Provider Control Panel and stop the VPS in order to update its status in POA, in a few seconds VPS should change status from 'Has problem' to 'Inactive' (it means that VPS is stopped), after that start the VPS (if necessary).
After the problem with the VPS status was resolved schedule VPS migration anew.