Related Profiles block
I think the problem lies in your contextual filter.  Presumably the teacher's profile page does not contain the taxonomy term ID in the URL, it usually doesn't unless you've done something tricky to put it there.

So: the view is looking at yoursite/user/[uid] and it thinks that the [uid] is the taxonomy term id (because you told it so), so doesn't find any matches and returns a nil result.

I'm not sure how to fix that, but hopefully this will help you troubleshoot.