Start by giving all the big cables a good tug looking for a broken one.
If the cables check good and the ones between the batteries probably will since you hear the solenoids clicking, you need to check the master solenoid. First see if it has any voltage on the small terminals when throttle is pressed. If you read a voltage on the small terminals then put your meter across the large terminals while voltage is on the small terminals. If the solenoid is closed you should read zero volts. If you read a voltage then the solenoid is bad.
Note: Raise the rear wheels when you do tests that require the throttle to be pressed.