Middle coin might not be installed in your game. It would be a coin door with 3 coin slots. Most only have 2 coin slots.

The keypad shares switches with the PF. If you have non working switches on the PF. You will probably have non working buttons on the keypad.

If your switches are not working right, check the switch plugs on the MPU board. Check the female plug for wires fallen out of the IDC connector. On the male pins, check for cracked solder joints.

You can check continuity from the PF to the MPU board past the connector.

I would say most likely have connector issue.

Come on man!! Bally testing is as easy as A B C! hahaha just kidding, what a pain that dumb keypad is.

I believe you want to be pushing the advance to begin tests, not enter. Enter is used when saving an audit value.

Here is a tip... do a factory reset. I have noticed testing NVRAMs, scrambled RAM data, or RAM from a different system can cause issues. Audits will have erroneous out of range values stored in them giving possible odd effects like not being able to start a game, not being able to add credits, and more. Go to the factory reset audit and set it for "65"(bally 6803 reset number is 65 and used in a few places). Hit enter to save the audit, back out of the menu to make sure it saved and power cycle. Next boot up will be default factory audit values.