Hi,
It's difficult to identify the problem without further information.
Basic checks: Is this a multi-poller environment? If yes, is NCM additional poller installed on the server with polling engine to which this device is assigned to? Aren't there any problems with connectivity between main Orion server and additional polling engines?
If none of the above problems exists, please create a support case and attach diagnostics from main and additional pollers.
Thanks,
Jiri