Not enough info, can you attach photo's of the back box boards?
GI's are fused off the interconnector board.

check for voltages at the fuses.
I Don't have a taxi but is there also a fuse under the playing field?

I would also suggest checking DC voltage at the coils, and there are also GI relays that you should check too.
I don't know if they control all the Gi's or not.
No Gi's in the back box either?

Also check the wire connectors at the transformer, all the yellow wires at the transformer are your GI power supply, that connector might be burnt.
might explain why no gi's at all.

As others have said using game schematics just keep following the coil voltage back until you find it working! (hopefully before you hit the transformer)

5p8 connector off transformer is for solenoids....goes to 5j8 on the Aux board at Fuses f7 and F8. So check the incoming AC at the fuses. You can't check AC to ground as the secondary isn't bonded, so red lead on the fuse clip F8, black lead on 5j8 pin 3. Then Red lead on F7 and black lead on 5j8 pin 8. If those are both reading higher VAC, then check DC F1, F4, F3, F6 and F5 for Voltages to ground. F4, F5, F6 apx 50 to 70vdc, f1 and F3 apx 25 to 40vdc.

For GI, connector 7j3 at the transformer. Yellow wires as mentioned above. They connect to the interconnect board at 2J6. On AC, check Fuses F1 to F4, against pins 1 and 3 on 2j6. If AC is good, then check other side of fuses F1 to F4 DC voltage to ground.

Attached Schematic for reference

taxi (resized).jpg