Unknown error comes when adding user to microsoft entra group using Add user group action spoke

[Santosh Kumar 1]

Hi,
I'm trying  to add a user to a group using Microsoft Entra spoke and Add User to Group Action. it seems the actual step is getting completed but after that an error comes as "Unknown Error " thereby the flow gets exited by throw error exception. 
Then I'm not able to know the actual error or not able to resolve the issue. Your help will be appreciated.

Here is the screen capture

 

Thank you,

Sanotsh