If you followed the Forza Motorsport 4 DLC download fix USB guide and still have issues, check these common pitfalls:
to "Save, Hash, and Resign" files on the USB drive before the console will recognize them as valid. Official Forza Community Forums Disc 2 Content vs. Digital DLC forza motorsport 4 dlc download fix usb
Many players believe they are missing DLC when, in reality, they haven't installed Disc 2. This second disc contains the bulk of the car roster and Autovista content. If you followed the Forza Motorsport 4 DLC
Many players have reported issues with downloading and installing DLC for Forza Motorsport 4 when using a USB connection. The problem can manifest in various ways, including: check these common pitfalls: to "Save