Hi Vijay,
Can you share a screenshot of the microflow? I think when you enable error handler on the REST activity, you should be able to configure a flow that handles the occurence of non 200-results.
Then the $latestHttpResponse can be used in the handling logic there, like this:
Good luck!
P.S. I cannot resist to mention that the custom implementation of ClientId and ClientSecret looks a bit weird for me, these terminology suggests that you should obtain a (short-living) access token at the Identity Provider instead of sending in a custom Header field to the Service Provider. Anyways: maybe wise to ask some questions about that.