I went back and re-read the earlier posts in this thread, and I see that csboling also suggested that you check the oscillator AND sync outputs on January 1, and you wrote back that you had checked the oscillators outputs but didn’t mention the sync generator outputs, so definitely a good idea to do that.
Also LZX posted the other day to ask people with sync gen problems to get in touch, since they know about the unprogrammed ATMEGAs. I would definitely talk to them and see about getting a new chip sent out. Even if that is the problem you can still keep working on learning how to program the ATMEGA, while you have a working video synth 