Hello, Sorry you're having problems. Offhand the unit not playing a disc is either a faulty disc itself, or your new Sylvania player has failed very prematurely (which is not uncommon as Sylvania is not know for reliable products these days since they were bought out).
I need to know, What specific disc is it you're trying to play? Is it an original or a burned copy? Is it new or used?
Does the disc you previously played with no problem work now if you try it as a TEST?
Please read my reply and postback to proceed.