Check that you don't have anything selected in any of the possible search options.
as an example, If you're beggining, you don't have any "R" class cars unlocked. But if you select "R" class cars in the Class section, the game will list only cars from that class.
And it will tell you that there are "No cars found under these categories"
So, check all the search options. Besides the ones you see normally (car maker, country, class, etc.), there are others you can use if you press R1 (or R2), L1(or L2, I'm not sure).
Unselect anything you have selected previoulsy, so the game will show all cars available so far, diregarding their class, drivetrain, country, maker, whatever ...
Hope this helps ...