Did you long rest in between sending Minthara to raid the grove and actually going to the grove to meet Halsin/prepare for the attack?
I think there's something weird in the game where doing ^ results in Halsin being (secretly) flagged as dead. Especially if you told Halsin to remain at the goblin base while you cleared out the 3 bosses.
Maybe check your quest log for rescuing Halsin and see if the quest mentions his death?
