I'm not entirely sure how to solve your problem. When this game was newer, some people experienced this with U R L races and magazine covers: they just seemed to disappear.
My recommendation would be to win another race or two, and see if they show up.
Also, it's possible that your car needs to be a certain star rating in order to enter. (Probably the number required for the last DVD cover in your last contract). Make sure you are driving your highest star rating car (stars are based on visual upgrades).
Some people have claimed to be stuck by this problem and never able to win the game.
XBL GT: dark minun Eye h8 UR lak uv spelinn an gramerz skillz.