Why can't I see or edit a grade set?

I can't see a colleague's grade set

Grade sets are private unless a school admin shares them. Ask your colleague to get it shared, or ask your MarkMate admin. See How to share a grade set.

I can see a grade set, but I can't edit or delete it

It's a shared grade set (it shows Shared with team). Only school admins can change shared grade sets, so that everyone's marking stays consistent. You can still use it in your assessments.

I can't remove a level

That level has already been used to mark work. Rename it instead, or leave it in place.

My grade set isn't in the list when I set up an assessment

Check that you switched to the right school and that the grade set was saved. Your grade sets belong to the school account you created them in.