Rob: In the GI test - do any of the lamps on that side work - or have you lost the whole string?

I don't know the machine - on my PZ you will lose the entire left or right side of the PF - not just slings and lanes? (My plugs are rooted too)

If some of the lamps are working (In test mode) - I would look at the PF wiring / earth?

If none are working - keep going with what Nino & Marty have said.