You need to mindread the mute goblin, did you do that. That alone will trigger something that is needed to continue.
Heed the voice in your heads warning though to finish any unfinished business in broken valley and Sentinel island as they are pretty gone after you get the tower. Only quests you can do in those areas after is go to the mine in broken valley and fly up to that boat stuck in the tree on Sentinel island. Oh and land on Lovis's tower in broken valley.
You'll have no way to complete any other unfinished side quests in those areas and they'll fail.