Your agent registers as offline and the following error appears in the Core AppRecovery.log, for example:
ERROR 2015-01-05T17:06:25  - Replay.Core.Implementation.Agents.ProtectedAgent () Verification ids is failed: Core agent id 64e232ae-375d-40e3-8948-4860838d2336, agent id 251ba194-1145-407d-b8f8-08a75c1cf2c4
Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 “Description of the Microsoft Windows registry” at Microsoft Support.
On the Core select the Agent.The Agent ID will be found in the Web URL, for example, https://Agent1:8006/apprecovery/admin/ProtectedMachine/64e232ae-375d-40e3-8948-4860838d2336/Details. In this case the Agent ID is 64e232ae-375d-40e3-8948-4860838d2336.
For Linux agents, please refer to KB259849