PC wont start with GPU plugged in

Mar 1, 2018
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EVGA 450 B3 psu
Geforce GTX 770 ACX GPU
Biostar HI-FI Z87x
I5 CPU
8gb g.skill ram

Had this build working before, tore it all down to try to upgrade (long story)
Put it back together while I'm waiting on parts, now when I plug in the GPU into any PCI slot it won't post. Starts, lights and fans fire up, then shuts back down, repeats.