Killed all the mobs in the last part of Uldur’s Cave, got (0 remaining) and then nothing happened.
Good morning WheezerX. 
This forum is for the very very old Diablo 1 game. Mostly for discussion between other players.
If you wish to report a bug with Diablo 4, you will want to visit the Diablo 4 forums. There is a bug report forum there.