I did do that. It seemed like a logical thing to do to me. I once bought a broken PC Engine Duo and fixed it just by unplugging stuff on the board and plugging them back in. That was a happy time! The Neo isn't giving me a happy time...Also just try unplugging the harness and plugging it back in first. I would just reseat all connections to make sure it's connected.
Unfortunately, to do continuity tests and switch parts if I need to, requires me going to the shop to buy stuff. めんどくさい...