Fixing a couple minor issues with a Nishijin A "Center King" model

[Praetorian]

Hi All, I just picked up my first machine, and it was a Center King as well. It seems to be in decent enough shape, but I'm having trouble getting the jackpot to activate when the ball goes into the center target. I can activate it manually in the back, and when activated it works fine, with the appropriate bells and disgorgement of balls. Any idea how I could remedy the problem? Thanks in advance!