I am unable to purchase designs for cars that I bought because my gamertag has been banned from.this feature. any ideas why. I only use the trainer for single player.
It doesn't matter there is a sticky on this topic you should've read it before you used the trainer: Link
If you use the credits cheat you'll probably get banned from all online features including buying and selling cars online and even downloading or publishing car designs.
I sent Microsoft a mail about it claiming that if I cheat in single player it's my business and my business only, they replied: since credit cheats effect online as well you are banned for good.
You know what is even more absurd, the ban applies to all forza titles maybe even future titles but I'm not 100% sure about it.
All I know is that I'm banned from forza 3 as well.