J1 on the power supply provides the GI power to the playfield. If you have GI behind the backglass, then it might be as easy as a connector issue. With the machine off, remove J1 and refit. Turn the game on. If there is still GI behind the backglass, bit not the playfield, CAREFULLY wiggle J1. If the playfield GI comes on, then it is a connector issue.
