I have these plastic snap on Disc protectors. I put it on one of my disks.. And the dvd player said error no disk. I have a Apex 660a. Any reason why this doesn't work?

I get very upset when my disks get scratched. Burning videos off to watch on my DVD player sounds like a good idea. Until the disks get scratched up. I know you can clean them sometimes. But doesn't that only get rid of dirt?