Why doesn't it work?

If it's electronic it sounds like the batteries are dead. Replace the batteries & try again.

One of two things is happening, either you have broken connections in the membrane switches of the keypad and should replace the keypad(which is most likely) or your main control board has failed in a way that it can no longer read signals sent by the keypad.

Probably the lamp

your getting ripped off try the defrost timer sounds like it is getting stuck, it operates on a 24 hour basis cycling between defrost, and turning compressor on and fan to cool the fridge

reinstall webcam driver for your operating system, will be ok.

The sounds like a systems control board problem, or the systems control has detected an issue with the camera. The only option is to return it to the place of purchase for repair or exchange.

Bad hard drive would be my first guess. You can easily test that by swapping it with a known good drive.

I had the same issue. It was the relay overload which essentially provides the extra boost to get the compressor going. The switch tries for about 10 seconds before giving up and then retries 3 - 4 minutes later. In the early stages of failure, eventually it will work and the compressor will kick on. But eventually the switch will fail and will just cycle through the 10 second attempt every 3 to 4 minutes. The part is about $35 - part number 67005560.

Try the disks in another DVD player. If they play with no problems in another player, then you have a hardware issue with your Sony. Nowadays, if it is out of warranty, fixing it is not worth it, because it is cheaper to replace, at least in the USA.