Here's one suggestion on how to proceed with your troubleshooting.

Locate the O relay coil on the schematic, and trace the wire that runs from the coil over to the right side of the page, where the 25 VAC power supply rail is located. On this O relay wire, You'll see some switches with a slash through them - these are normally closed (NC) switches that need to be making good contact for the O relay to energize. Check these switches and see if any of them are out of adjustment and not making good contact.

Each switch may be marked with a letter, meaning it is located on, and actuated by, the relay with that letter. Or, a switch may be marked as being part of one of the mechanisms, such as a stepper.

If you want assistance in looking at the schematic, you can post a pic showing the circuit for the O relay coil. A snippet of the schematic that covers the area from the O relay coil over to the 25 VAC power rail on the far right would be the most useful. Please note that you should avoid posting a picture of the entire schematic, as Gottlieb schematics are under copyright protection.

- TimMe

RSTrunks, if you don't have a schematic, here is my Super Soccer. Assuming the 4 player version is similar when it comes to the outhole, this may help:
IMG_4129(1)a (resized).jpg
The upper green line shows the circuit for the kicker - which you say works when manually operating the O relay.

The red line shows circuit to operate O relay. As TimMe says, there's a number of switches that have to be closed for it to pull in:

From right to left on the schematic:

a NC (normally closed) Anti-Cheat Switch (the right hand side of this leads to the 25v TimMe mentions, via a 15A fuse that is (on mine) a Red wire with Green trace (the reds often fade!)

Motor 2B

Motor 1C

NC on the GX relay

Ball Return Switch (you checked this one)

A make/break switch, that needs to be closed at zero position of the bonus relay (meaning bonus has to count down to zero for this switch to close before kicker fires)

NC on relays E, SB1 and QB

So, I would check the easy ones first (and the ones that move more than others) - the two switches on the score motor, and the zero position switch on the bonus relay.

Next clean the NC switches on all the stated relays, or use a jumper wire to start to eliminate switches until you find the culprit.

I know from very recent experience the switches on the large relay bank are a pain to adjust - hence I'd leave those till last, or use the jumper wire to see if you can narrow it down.