pin 1 is on the right side of each board as your looking at them mounted in the head. Make sure pin 1 goes to pin 1 on each board, same with pin 2, 3 etc. Pin 33 and 34 will be left not used / not connected on the MPU (on the far left).

When you had the sound board plugged in wrong it may have scrambled the RAM chip. Reset the current credit count audit(i think it is #5) in test/audit mode. A bad value can get saved there and possible for that will not take coins or start a game until you manually clear the current credit audit.

There is a circuit that should mute the sound board at power on so you don't get the power on cap charging up noise. They changed how this circuit works over time. There should be pinside posts about this, maybe even pinwiki has some info if you want to get into it. May be worth fixing other stuff first.

I assume the rebuild kit includes capacitors, connectors and maybe the trim pots. Probably not a bad starting point. In solenoid test you should hear noises. See if any of those sounds are missing.

Not sure if Hot Hand has a "chime vs electronic sound" MPU dip switch, but worth checking the manual for it. Looks like your board is missing the chime circuitry so it must be set to electronic sounds or you will get no sound.