I'm newish to EM's and would suggest you read the em section of the pinrepair.com website a couple of times (will explain how to set to free play !)
Also clean and check all switches (including playfield) for correct gaps and operation.
Manually set some score reels to non zero, turn on and see what happens with the score motor - should turn a bit, reset score reels and eject ball. If score motor keeps running, check switches again. If score reels don't reset, check EOS and other score reel switches for contact and operation.
I recently solved a major issue with my 77 Williams Big Deal buy finding a loose screw where it shouldn't have been.
Good luck & enjoy the journey !!!
Cheers.