I would wager it needs to be cleaned more thoroughly than one of those cleaning discs will do for you or the laser has gotten out of alignment somehow.
You could try resetting it , should be a little button on the face (like on a watch) that you can use a toothpick to push in .... But if you have the security code activated you will need it to turn the HU back on .
If it won't read any discs, the little laser eye might have come loose in the HU. That's happened to 2 of my kenwood HU's. Pretty ****ing gay if you ask me.