GI - Could be as simple as a fuse - There will be a informational card in the backbox denoting the GI fuses. Check them all.
So – tell me.
These games use 5 fuses for the GI ???
It appears that 5 x 5A Slo Blo’s are required for the GI ??
So – if ONE of the 5 is out , then 95% of the GI could be out ??
They may look "good" but they could still be fried. Remove one end of the fuse and check with a MM set to "continuity"..Now lets see how many fuses are good !
The other thing to check which Dave mentioned - connectors - Do they look healthy ? Refit them.
Also check under the playfield for loose wires on the GI lines. You can tell that they are GI pretty easy as they are all connected via braid.