I finally solved the problem with the GRT Sport EFIS not coming on when power is applied. I spoke with Carlos at GRT as I was testing the unit. The ground and power connections tested out properly.
Carlos said that perhaps a loose wire from the connector was touching something and grounding out. I asked if the magnometer wires could be a problem if they were touching each other or something else. Carlos said that coule be the problem. Sure enough, I traced the magnometer wires aft and found them taped together at the ends. I removed the tape, separated them, turned on the EFIS and it worked !
Matt Deem helped me by holding the radio antenna in place while I screwed it in place from above.
I could not find all the hardware for the second antenna.
