How can I fix my portable DVD player?

My Astar (brand name) PD-3010 stopped working. It is less than one year old but they will not repair it free of charge because I no longer have my purchase receipt.

When I put a DVD in the player, it cannot read it. It makes several attempts and then says "bad disc." I've tried many different discs so the problem is obviously with the DVD player and not the disc.

Before I return it to the manufacturer (they're asking for $25, not a large sum but it's a hassle) I'd like to see if I can fix it myself. Thank you.