So the direction the switches are shown in the instructions is wrong. The pins have to be at the top, not the bottom (that’s where the holes are in the PCB). Double-checked it just to be sure I hadn’t done something odd.
Tip: you can plug the PCB into your computer and check each switch works as you plug it in :)
(Careful you don’t bend the pins when placing the switches. Make sure they go straight into the holes.)