Originally Posted by: DawidSM 
Is this achievements are broken?
Painting by Numbers (10)
Earn 1,000 credits from the community using your paint jobs.
Pro Tuner (10)
Earn 1,000 credits from the community using your tune setups.
Master Tuner (15)
Earn 15,000 credits from the community using your tune setups.
Museum Quality (15)
Earn 15,000 credits from the community using your designs.
Colour of Money (20)
Earn 30,000 credits from the community using your designs.
Artisan Tuner (20)
Earn 30,000 credits from the community using your tune setups.
Apparently, the game is no longer supported because they no longer have the resources to go back and make a few changes so you can earn credits when someone else uses your design/paint/tune, etc.
Kinda sucks because the achievement tracker shows I have made progress, but I can no longer earn credits therefore the achievements are unobtainable.
A first-party studio, with a game on a current-gen console, can't somehow fix what is theirs. Microsoft own Turn 10 Studios and the Forza IP, but this was their response to someone else:
"I'm sorry, we, unfortunately cannot turn back on the servers, we do not have the ability or support to do so."