Same happened to me. Did you use the cheat menu at all? It seems if you use cheats for restrain potion to do bernard quest, you miss out on learning restrain potion (strong) at your hut after you turn in More Potions to Bernard, so Othra can't give you the quest. Or something along those lines, I forget the specifics.... I had to restart my save and not cheat with potions to get it to work.