After each co-op ( i only play brutal ) it shows all the experience gained, however its not showing any progress bar with level, nor does it show in the ascension screen when i select a level 15 character. It shows 0/0 Ascension XP. I have not noticed a level up in quite some time. Have even gone back and checked after the last three matches just to see if it happened in the background and maybe the UI is bugged. Nothing.
I am currently Ascension 95. I have all characters level 15, and i am most often playing Zeratul with Prestige level 3 selected: Herald of the Void. I have been using this prestige for months though, and this change is relatively new.