Check again the way it is plugged,,, be sure that it is plugged correctly and in the right way...also take a look to see if the dvd shows signs that it works...I mean it takes the play ...in this case it may be from the tv ...if u use a rca cable be sure you press the TV.av button on the tv's remote ..or after case..you select the Hd in from the menu ..or the tip of cable u use...
in case that the dvd is not showing signs that it takes the disk ..this is a malfunction on the device itself..and look in the menu a the reset command.. if you do not find it takle a look in the manual ...

First thing would to be to open the disc tray. Then remove the disc. Then blow real hard inside a few times. You can also use a can of compressed air or air duster. This will blow of any dust built up on the laser lens eye.

If you feel up to it, you can can take the top cover off, then clean the glass laser lens eye with rubbing alcohol and a cotton swab.
Let it dry and try using and watching a disc with the cover off and make sure it is continuously spinning. If not, the laser lens, motor or circuit could be faulty.