the service panel buttons have their own header on the PCB, from your picture it looks like it's plugged in check to make sure the disconnects underneath the buttons haven't gone lose, if ALL of them aren't working then chances are the ground wire is bad. these can sometimes get pinched in the door so after a visual inspection I'd start with testing continuity on the ground wire. it could even be bad on the wire at the connector as those IDC connectors are trash and tend to be flaky.
so in short:
visually inspect the coin door harness for damage or loose wires on the buttons as well as the connector on the game board
use a multimeter to test connectivity between the connector on the game board and the buttons, starting with the ground wire.
When I got my MK2 cabinet, the Polo in there was phenomenal looking after a cap kit, and the remote adjustment board let me dial everything in without having put my hands in impolite areas. The pincushion board on it also helped me adjust the geometry a lot better than I could on my K7000. The ONLY issue is that the vertical linearity is just slightly off, but that's at the very, very, very bottom of the screen and the only time I can even see it is when text scrolls like at the start of Hyper Street Fighter 2.
I find that my CPS1, CPS2, and CPS3 boards all are very slightly different in image dimensions, so when I switch them around I need to make very slight adjustments to fill the screen. With a K7000 that's damned near impossible to easily do from the front of the cabinet. With a Polo, it's simple as pie.