My first concern is you meaning "WinForms" multiple times. Test Studio does not support testing pure WinForms applications, only WPF based applications. If your recording appears to be working just fine then maybe it really is a WPF based application and not WinForms. When you manually run your application, does it appear in the list of Active WPF Applications as shown in this screen shot?
The other technical problem is that Test Studio needs to be able to directly launch the application in order for us to inject our test automation hooks into the application. Currently we don't have the ability to "Run as a different user" in order to execute the application with impersonation as another user in another domain.
The only work around I can think of for today is to execute the test once when logged in as user A then run it again when logged in as user B on a different domain.
I have created a feature request for "Run as different user" option which you can track here.\
the Telerik team