1. Check whether this client is in "Blacklisted Host Computers" filter or not on NS side.
2. If SMP version is 7.5.x but client version is 7.1, then make sure that you have turned on "Legacy Agent Communication" option on NS side to allow 7.1 agent to communicate with NS.
3. Try to refresh policy on client side and check Symantec Agent logs in C:\ProgramData\Symantec\Symantec Agent\Logs ⇒ there should be a message how request of policy was completed.
4. At last point, you can try to reset a client computer GUID via cmd on client side
- C:\Program Files\Altiris\Altiris Agent\AeXAgentUtil.exe /ResetGuid