Since the last major update, my husband keeps encountering this problem– particularly (but not exclusively!!) in Vvardenfell and Stonefalls.
NPC accepts Tribute match, and literally all NPCs disappear. No more match or interactable NPCs. Porting to another zone and back sometimes resolves the problem, but not reliably.
Aus der Engel Ordnungen is a bald, bespectacled, Dunmer vampire with an affection for Dwarven tech. She cannot hear you scream. "For beauty really is nothing but the beginning of terror..."