I don't have those game pcbs nor I know the specific pcb from experience, but let me give you my 2 cents to start troubleshooting.
Check you power supply first, especially for +5V.
You should check for +5V not only at the PSU, but also far from the power connector in the game pcbs.
Then check your connectors. Unplugging connectors and then re-plugging is generally sufficient to restore a lost or "floating" electrical connection. It could also break corroded pins, but I don't think these boards suffer from corrosion.
After that you could start considering a pcb fault.
Being that you have more than one pcb, swapping them could give you good informations and help troubleshooting.