For some reason, after I exited a battle, my follower wasn’t there. It hadn’t fainted, it just wasn’t there. I tried switching it for another, but that didn’t work. I also can’t use tesseract to get through the cave to the south of Amphitrite city.
Try loosing on purpose to make all your mons fainted?
Edit: Not an ideal solution for nuzlockers.
That worked, thanks mate.