Ideas
Same! I don't have the Adventure Awaits pack but this has been happening for me since the game update a couple months ago (when Businesses & Hobbies released). I don't have any cc or mods either. This is important to my gameplay too bc I also have a legacy save where I have them paint portraits of each new generation. I still can see my old portraits (painted pre-update), but any I try to paint now always turn white once I log off the game.
I've tried saving the paintings in rooms and uploading the rooms to my library; deleting the cache; starting a new save file; pretty much everything. But no matter what, I can't have reference paintings in any of my saves. Its so frustrating and while I'm not glad other ppl are having the same problem, hopefully this helps elevate it to EA to fix.
Yeah I also tried all those things as well with same issue 🙃hopefully it gets fixed for all those with the bug