Ok I can finally play DVDs, but I don't see the "Play Disc" button; which I don't care much about, so that's ok.
The problem was that I had a CD/RW, and a DVD/RW on the system. It took the CD/rw as the default, but it wouldn't pick up the DVD/RW. My solution was to remove the CD/RW, and just leave the DVD/RW.
If someone knows how to add the "Play Disc" button, let me know.