Just exchange it for another one. It might be a bad drive.
Also, have you checked the bottom of the disc to see if any data was actually burned to the disk?
Does it recognize a dvd movie? If it does, then there maybe a problem with the burner not burning.
What store did you buy it from?
When you say it won't read a burnt dvd that was previously burnt, do you mean by another drive or something?
What happens if you burn a disc with the Pioneer? Does it read back in the Pioneer and any other dvd drives you have?
Do you have another dvd burner in your computer and does it work? If so, I would sent the Pioneer back and get a new one. I'm sure it is just a bad drive. It happens