Are all the score reels in the backbox set to zero? If not, you'll want to activate them by hand to set them to zero. If that fixes it, you'll need to clean or rebuild some/all of them to get it to start (and score) consistently.

I suppose the next thing would be to check that all the 0-position switches on each of the score reels is making good contact. If you cycle the score reels by hand, you should see the various switches open and close at certain points in the reels rotation. Make sure they all are opening and closing properly as the reels turn.

Does it keep kicking the ball out, and eventually go to game over? Have you checked the ball count unit?

Check the outhole switch adjustment

Is the Ball Count also increasing as the balls go through the trough? As it should stop on the 5th ball, if the Ball Count unit is working. It is possibly a bent trough switch, (the one between the ball return kicker and the shooter lane) also a possibility of a broken wire between the trough switch and the ball count unit, you will have to check these at least. Has the Ball Count jammed up?

It can also be out of position, a lot. There are 2 stops on the stepper gear on the backside, that have to open and close the switches/contacts on the backside of the unit.

NEVER use WD-40 in an EM machine. WD-40 is not a lubricant or cleaner, it gums up over and time and worst of all is highly flammable. A spark might set off some of the residue left over and start a fire.

http://www.pinrepair.com/em/index1.htm#lube

I use dry paper towels for cleaning.

If there's a lot of grim my go to is 99% isopropyl alcohol and a lot of cotten swabs. Just MAKE SURE it's at LEAST 92%. I find anything lower leaves a white residue behind that can cause electrical havoc. If you do use it, make sure the area is well ventilated and wait at least 15-30 minutes after use before turning the machine back on. While I've never personally had issues even after 5 minutes, better safe then sorry.

While you generally don't want to lubricate anything, if need be the only thing you should use If Teflon Super Lube Synthetic Grease. https://www.amazon.ca/Super-Lube-21030-Synthetic-Grease/dp/B000XBH9HI
And if you do, only apple a little to the rivets at the back of the ballcount unit so the plate travels more smoothly. Don't use it on the shaft or anything. Stuff works well, it was able to get a stiff gottlieb AS stepper working again and saved me the headache of trying to take it apart.

I have good luck with mineral spirits. It cuts through grease and grime, has a longer working time than alcohol and doesn't leave a residue. It works well with rags, Qtips, old tooth brushes, dental floss (for tight spaces), etc.. I keep some in a handy spray bottle.

Sometimes I'll use citrus based cleaner in an ultrasonic cleaner if I'm going to disassemble everything. It cuts way back on the elbow grease.

I find that if I thoroughly clean everything (which usually means disassembly, cleaning, reassembly, adjustment, etc.) that I rarely need any lube in an EM game for home use. I usually reserve lube for things that have wear that I can't fix or grease/grime in places I can't get apart which isn't very often.

/Mark