Going to state a few obvious things which I'm sure you will have checked, but just in case.....
Press the mute button a couple of times to check that it isn't muted
Press the SRC button a few times to cycle between CD and radio to make sure the right input is selected
Check the volume is up (sorry!)
If none of those work it's probably time to buy some radio pullers from Halfords and check the connector on the back of the radio / CD. I have to say though, it's a very snug fit and unlikely to drop off, but worth a look anyway.