Blank user ID issue in Rest Request

We have an issue where the Rest Request is going with a blank user Id which unfortunately is not retrieving the results.What can be done here we see request format is proper!

I would recommend the following steps to troubleshoot,

  1. Use the Tracer to validate if the User ID is passed to the data pages/Request DT mapping correctly.
  2. Enable the REST logs to capture the request and look for any clues.