That's a bit tricky -- 40 down 2 is a big number of combinations. We get about 7k ohms on 18,19, 20 (upper right in my image -- I'm not sure what the correct numbering is!) and the same on each of these to most every other pin. Except pin 1 (upper…
Oops -- we tested across the 5v in to ground, not the 3.3v out and ground. I'm afraid to plug the main board back in to do that test.
We do have continuity between those pins on the AVR, although the solder joints are clean there. Is that a fault …