Is there a pause after you go through the ramp? Maybe just that sound is corrupted on the rom?

Does the playfield bonus grid and backglass show the 3-2-1 countdown? It should. So if it's doing so, I would suspect a sound issue as Toyotaboy suggested. If it's not, perhaps it's an issue with the shuttle switch, as that's what actually triggers the effect. If you hit only that first (shuttle) switch but don't have enough momentum to send the ball to the second switch on the ramp, you get a countdown which aborts, and no ball release. I'm not sure what happens if the first switch is missing and then the second one is hit...? Just offering some troubleshooting refs.

If you half ramp it does the center post pop-up? This sounds to me like the ramp entry switch connector is not connected, not registering, missing or broken in some way. You can still start multiball by hitting the back switch but the game won't pop the center post and if I recall, doesn't do the countdown if it doesn't register the front switch.

That feature is not selectable AFAIK; it's kind of integral to the game.

Let's see, from memory I think there's a 2-pin molex connector for that switch under the playfield, feeding out under the shuttle, so make sure it didn't somehow come loose. There's probably a diode somewhere if not on the switch itself, so check that. You might also remove the switch (disconnect the wiring) and use a meter to make sure it's good (check for continuity when you close the contacts) - that last step would confirm that the switch itself is good and not just finally worn out.

Glad to hear it's working... sometimes the easy "mystery" fixes are the best, the machine just wanted some extra attention