To ensure that the OfficeScan clients will get updates from the migrated Update Agents, you must re-assign the "Act as Update Agent" privilege to them in the new OfficeScan server. 

Do the following:

1. Log on to the OfficeScan management console.
2. In OfficeScan 10.x, go to Networked Computers > Client Management and then select the Update Agent from the client/agent list.

   If you are using OfficeScan 11.0/XG, go to Agents > Agent Management, and then select the Update Agent from the agent list.

3. In OfficeScan 10.x, move the selected client by clicking Manage Client Tree > Move Client.

   In OfficeScan 11.0/XG, click Manage Agent Tree > Move Agent.

4. Select Move selected client(s) to another OfficeScan server or Move selected agent(s) to another OfficeScan server (for OfficeScan 11.0/XG) and then provide the IP address and port number (8080 by default) of the new server.
5. Click Move. The client will appear in the new OfficeScan server console. After the move, the client/agent does not have the Update Agent privileges.

To assign Update Agent privileges to a client/agent:

1. On the OfficeScan Management console, select the client and then click Settings > Update Agent Settings.
2. Select the clients/agents that can act as Update Agents, and then click Save.
3. Add the Update Sources to the new server by going to Updates > Networked Computers > Update Source.
   If you are using OfficeScan 11.0/XG, go to Updates > Agents > Update Source.  
4. Assign the IP ranges that should the Update Source and then save the changes.

After granting the Update Agent rights to the client/agent, you can also migrate the Other Update Source (OUS) list from the original server to allow the migrated OfficeScan clients to get updates from that particular Update Agent.

If the issue persists, please contact Trend Micro Technical Support.