When I speak to Kaessi in your new keep (Start of act II), I see dialogue reply choices, but when I press on them nothing happens. I saw same issue when trying to google my bug, but the guy who post it, did not receive any replies. I already tried verify/repair files (I have GOG version), switched to borderless resolution, run game without mods, but still nothing.
Because of this I am locked out of that DLC Tiefling quest.
I came to this location again after “Troll Invasion” event started and dialogues started without any issues.
I guess there is some connection, but who knows.