Forza Motorsport 4 reached "end of life" status on September 15th, 2015. Forza Motorsport 4 and its associated DLC will no longer be available for purchase.
After September 15th, 2015, players who own Forza Motorsport 4 can find owned content in their library to download and play the game and its associated content as normal.
Unfortunately, we no longer actively support Legacy Forza titles. Limited support is still available for matchmaking and leaderboard services; however, access to this functionality is not always guaranteed.