You'll get more relevant responses in the SS forum.

Could be a couple things. Is the switch registering in switch test? If so, is it registering with a ball or with your finger?

If the switch is not registering with your finger, then check and adjust the wiring and switch. If it is still not registering, then replace the switch.

If it is registering with your finger but not with a ball, the adjust the actuator arm until it registers with a ball.

If it is registering with a ball, is the coil firing? If the coil is firing, is the plunger in the coil binding?

If it is binding, disassemble the mechanism, clean all associated parts and replace the coil sleeve.