What you were expecting to happen, and what actually happened:
I did the quest to unlock Hierophant, raised it to level 20, unlocked its 3 traits. Now the last class in the list, Warpriest, does not have its class level displayed on the class selection tab, regardless of the context under which that tab is being viewed.
Restarting the game from scratch does restore the display. This suggests there is a bug in the class-unlock code, which should be addressed.
I would check this myself at the next class release, but that’s not my job. It’s also much easier to check, and can be done immediately, by a competent, in-house QA engineer.