I have a new Xbox 360 and can only play my Rock Band DLC when I'm connected to the internet. How do I play offline?
Good news! If you've recently purchased a new Xbox 360, all your old downloadable content isn't lost! You just need to transfer your license so that you can download it to your console. Once it's downloaded to your console, you'll be able to play offline again. Otherwise, your console will need to be constantly connected to the internet to verify your license. You could also be having this issue if you've had a new harddrive installed in your Xbox 360.
Fortunately, this is an easy process. Xbox 360's License Migration page will walk you through the steps. Visit the following Xbox support website to begin the migration process: