The Microsoft Exchange Unified Messaging service on the Mailbox server received a PlayOnPhone request from user "%1", but ...

The Microsoft Exchange Unified Messaging service on the Mailbox server received a PlayOnPhone request from user "%1", but the telephone number "%2" can't be dialed as specified. To correct this issue, make sure that you've correctly configured the dialing rules on the UM dial plan and the dialing restrictions on the UM mailbox policy that's associated with the user. The UM mailbox policy and user must also be enabled for Play on Phone.