Free play class restriction?

I have always been able to use any car in free play. Now when I try it will only allow me to pick b class and under cars and then it says the car has to be modified to a full b class. Why is my free play all of a sudden no longer free? Thank you.

What settings are displayed for each one of the fields?

Are you sure you are in Free Play? I have never got that message and I drive in Free Play every day. The AI drive stock cars with no tune or upgades no matter how you setup Free Play. You can set the class and division to ANY and that will let you drive any car in your garage.