Save Failed - Add/Edit Application Assignment

Hello All,

I am experiencing an issue while adding and editing app assignments. I recently upgraded WS1 from 1907 to 2001 patch 25. Post upgrade, everything is working except application assignments. I get "Save Failed error" every time. I cannot even edit the existing assignments and change the license allocation. It does not matter what kind of application it is or what platform it is for. It just fails every time.

VPP and APNs are fine.  Test Connection Over HTTP/2 - Successful.

Any suggestions ? Anyone knows of API calls to add and edit applications ?

Thanks