I bought ME2 recently on Steam and activated the Cerberus network DLC. The files it gave me to download don't detect ME2 as being downloaded. Anyone able to help with this?
Well, try re-downloading and re-installing ME2. I know it's annoying and time consuming, but I have experienced this Steam DLC problem with multiple games(including ME2) before, and this fixes the problem every time.
How to re-download Mass Effect 2
NOTE: If you have not already synced with Steam Cloud, do so BEFORE you delete ME2, otherwise all of your progress and game data will be lost. See Steam Forums for how to sync with Steam Cloud. Hope this helps!