On my PC account I’ve been getting this “cannot change Difficulty” pop up message when I travel into dungeons solo.
It goes away when in a group finder group. But it keeps popping up while I solo farm a dungeon and sometimes even in overland the message still comes up.
I go into a dungeon. Finish up. Port out. Change from normal to vet or vet to normal. Travel back in to dungeon. This message keeps popping up at seemingly random times.
It’s not exactly game breaking, but quite annoying.