It works now. I called ESRI to help me with this and we followed these steps:
1. As mentioned create a GlobalID and GUID
2. join the two tables to relate in order to calculate the GUID field with the GlobalID values
3. Relate GlobalID and GUID fields
4. Publish the service.
The main problem I had was that I was not too sure how to relate globalID and GUID. the join solved it for me.
Thanks,
Alex