failed to acquire Quodra Virtual Data Center Workstation license

I am running a windows 2016 server with nvidia Tesla P4 and failed to acquire a quadro vitual data center workstation license.The nvidia license server has been configured (correctly).
At my license server I checked the server log files and it reads like following:

14:40:24,830 WARN [6C92BFAF02A0] Unable to handle request for feature GRID-Virtual-WS-Ext 2.0 count=1. Reason: FEATURE_NOT_AVAILABLE.
14:44:17,388 WARN [6C92BFAF02A0] Unable to handle request for feature GRID-Virtual-WS 2.0 count=1. Reason: FEATURE_NOT_AVAILABLE.
14:44:19,457 INFO [6C92BFAF02A0] Successfully handled request for feature Quadro-Virtual-DWS 5.0 count=1 correlationID=d9d688af-e0d7-4cc3-a316-e18277e15ee0.
14:44:21,812 WARN [6C92BFAF02A0] Unable to handle request for feature GRID-Virtual-WS-Ext 2.0 count=1. Reason: FEATURE_NOT_AVAILABLE.
14:44:21,813 INFO [6C92BFAF02A0] Feature Quadro-Virtual-DWS 5.0 was returned.

And this message repeats its self and the client says it is "acquiring license for quadro virtual data center workstation."
I notice that one message in the log present above says "Successfully handled request for feature Quadro-Virtual-DWS 5.0" and I think the authentication should have been succeeded. So why is the client still unlicensed?

Could someone please answer (maybe solve) this question? thx a lot.