Realm of Terror Achievement

I have completed the realm of terror achievement in champion season journey multiple times but will not check off. I’ve completed everything on all areas but the realm of terror not checking off us holding me back from completion, any ideas?
I’ve done it on t10 t11 t11 t13 and t14 with no success

Are you doing it on the proper Torment Level? Be sure to select that and then do the milestone. It takes T 10.

Here is a handy season tracker