Board Thread:Questions and Answers/@comment-24989822-20151030095606/@comment-679780-20151101122943

Where exactly did you download Sonic Adventure followed by DX as a DLC? Do you have it on a digital distribution platform?

I'm thinking maybe you have to activate the DLC by checking the game in the Game Library of your service and making sure the DLC is ticked or activated it on some list. Depends if you got Sonic Adventure on a digital distribution platform like Steam.

It's only then any of your games will recognise and use DLCs you downloaded for said games.

Though Steam only has SADX and not a very good one.