I do in fact do assign it to a variable (stringUserID) and then assign it to the "Find User" service operation Universal ID in the filter. It fails there too.
Paul, I have not checked the AWS_Assigned_ID in the data stream. I do see a valid GUID assigned to stringUserID from the creator_ID. So, I guess I need to amend the title of this topic to "UserManagerLookupService.Find User not working".
In fact, I use this same activity in another process, a custom render process, that works just fine. I looked at the GUID for both processes during playback and they are identical. It works fine in the custom render. In this other process, I see an error "Variable: null not found". When I expand the details, I see "com.adobe.workflow.template.document.VariabeNotFoundException: Variable: null not found".
Am I missing something?