I just created a custom venues with Art activities sucha painting, woodworking, flower arranging and when I plan a gateway on that lot, each role get to their activity except the ones supposed to paint...no one is doing the painting activity AT ALL. If it's the sim from my active household, I can "force" them to do the activity, but for the other acitivities later, they automatically engage into it, so I don't know why painting doesn't work.
I don't play with mods (I removed UI cheats that was the only mod I got, I removed it yesterday).
