Coby DVD shows Invalid Disc \r\nHELP PLEASE

Did you make the disk if you made the disk your computer has to give it a digital signature so the DVD player can read it if you're using a regular DVD then I would very carefully using rubbing alcohol and Q tip clean the actual laser I would be very careful doing this if too much rubbing alcohol is on the Q tip it will ruin the laser you can also try resetting the DVD player by taking out the battery and unplugging it from any power source and leave it that way for at least 20 seconds to a minute if that doesn't work you might have something else wrong

my coby portable dvd player is showing invalid key on screen, what does it mean??