I Have been having an issue with receiving my credits recently on Forza 5. Every time I go and do the Free play racing to try and do some money grinding, it never gives me my money. I usually set the laps anywhere from 20 to 50, but even when I have it at only 1 lap I still don’t get any money . Here is a video of what it does to me after a race 1 lap around the Indianapolis Motor Speedway in my Hennessey Venom GT - YouTube PLEASE FIX THIS ISSUE it’s just a weee bit aggravating.
I think that you rented the car. Renting a car for free means that you can’t earn XP or credits.
I’m pretty sure you need to race against the AI to earn credits and XP. The game will not reward you for just racing by yourself around the track.