Also, Physical Agent showing 0 disks in the 'Disk Selection' screen of the Task Scheduler.
Possible Scenarios include:
a) The service is not credentialed with the user with the correct permissions to run the service; which would also lead to
b) The "Quest Physical Client Service" is not started
Make sure the proper credentials are used for starting the 'Physical Client Service' and make sure the Physical Client Service is also running.