"Group By" using Relationship Field

We’re attempting to build a view that uses “Group by” on a relationship field and it’s coming back with no values. Is this not possible? If it’s not possible, then relationship fields should be removed from the list of available options to pick from. Otherwise, is there something deeper going on here?

Actually, I see now that filtering by relationship is possible, I’m doing it in other apps. It just doesn’t seem to be working in this one. I try to Group by a relationship field and the view shows nothing even though there are related values there to use. This is the only relationship field in this particular app so I can’t test another.