The buttons are either conductive rubber, or, more likely, have a conductive ink or paint on the back side. They press against interlaced traces on the PC board, effectively shorting them out like a switch.
They are very similar to other rubber keypads, notably the ones on your TV remote controls.
I have repaired these in the past by a couple of different methods.
Buy and use a kit like this:
This one is from Amazon.
Or, glue a patch of aluminum foil on the offending button with rubber cement, carefully applied superglue, or another adhesive. In the past I have also used adhesive alarm system foil window tape.
The kit is ~$22. The foil is essentially free, depending on your glue selection. The keypad is $12.
You choose...
It could also be that the contacts and button are just dirty. You might try disassembling the console and cleaning them first.