Unable to produce a masterpiece

I am on the last part of the painter aspiration and I have been unable to produce a masterpiece for a few weeks now. They used to be quite often - at least a few times a day (IRL) but it has dropped off significantly, why? Also when paintings even at max painting level they are only fetching a couple hundred simoleans which is a lot less than they used to be. Can anyone explain this please. I have no mods or cc's and my game is up to date.

Many thanks