I tried some DVD－R/RW discs on my AVN726EE, but they wouldn't play back. Could you explain why?

When using a DVD-R/+R/RW disc, note that only a disc whose contents were recorded in video mode can be played. Discs whose contents were recorded in VR mode and audio mode cannot be played. Please also note that the region Code of the DVD must match that of your country's or is that "Region Free" for the disc to be played back by the system. If not matched, play back is not possible.