How to handle when the power supply does not work?Then just of the top of my head,
if you have a push button engagement, you must have an electric solenoid that will engage either a wet clutch or a dog clutch. doodle cricket
Without a service manual it's hard to say what is going on.
Roughly if you can find the solenoid and see if it is getting power, if it is can you feel it engage (clunk) when switched on.