06 Trailblazer wont start after new head unit installation

[ecksbingo]

This would be the bose+onstar model. I installed everything correctly, the radio was working fine. I used the metra gm11 audio interface and the car did turn over once and now I get nothing when the key is in any position.  No security light, I checked most of the relevant fuses and relays and everything seems fine. Not sure where to look next.

[Jsdirt]

If I were a betting man, I'd say there's a problem back there with some communication wires. Didn't think they had that back in '06 but anything's possible. Only plausible explanation, unless an accidental short of a power wire blew a fuse.