What else can I check?
I'd try... Check there is zero resistance between pins 8 and 22 of the AtMega Plug in power, and make sure you get +5V on pins 7 and 20 of the AtMEga With power still on, check you get > ~3.5V on pin 1 of the AtMega Check the LED lights up if you take out the AtMega, apply power, and plut a bit of jumper wire between pins 7 and 19 of the empty socket
3. Check 0.84v on Pin 1