unsupported format

My back up DVD copies won’t play/start in my computer or my stand alone DVD player(s).I get a disc error message on the stand alone and adisc with an unsupported format message on my computer. Is there someone who is familiar with this? I thought it may be the discs, (Verbatim DVD+R)so I tried a different brand (Maxell DVD-R). I always burn at 4x, but this does not seem to make a difference. I was making a backup that turned out successful and then the next attempt came out with the above problems….