It looks like you may have that wire tab that broke off. It can come off or the switch "nub" may have broke or wore down where it fell off. Anything in cabinet? Surprised you never had an issue before.
Wire tab should be similar to this: https://www.marcospecialties.com/pinball-parts/5647-12073-32 but don't think it's the part number you'd need. Can you unscrew the upper most switch and take a picture for us too?