Replying to Memory Card Recovery Help

So I tried to import my footage that I shot yesterday on my Canon 7d onto my computer to begin editing. My Card wouldn't show up on my mac. Also when I try to open up the card on my camera it says, "Card cannot be accessed. Reinsert/change the card or format card with camera." I've shot video a ton in my life and have never had this problem. I tried downloading different card recovery programs on my mac, and they all have a trial version where you can only recover 2GB worth of data, unless you want to pay for the full version. However, when I used these programs I was able to view the files, so I know that they're still recoverable. Does anyone know a recovery program on mac that is free and can recover around 20gb worth of data? You're help would be a lifesaver. Thanks

Long Story Short: What free card recovery program can I use on mac?