Yes, it's an allied realm.
Is it possible that another diplomat is quietly undoing your work?
I don't think so, but would that make a difference anyway? The issue is not that the diplomatic actions as a whole are having little effect (although that is also the case), but that each individual attempt is failing. Whatever dice roll is used to determine if the specific diplomatic action succeeds (or at least has a greater effect than the worst possible result) is failing every time.
