When Agents are moved between Scalability Servers, the agent is marked as "LOCKED MY MOVE" which means that the agents are in a moving state from the old Scalability server to the new scalability server.
Client Automation - All Versions
The agent would be in this state unless its installation history/properties is moved/updated from the old server DB to the new one. Now, when the agent is in this state you can not send any jobs to it.
You also have to make sure that the old server to which the agent were reporting is online.
After all the installation history is moved from the old Server to the new server DB the agent would automatically return to normal state.