New ECM a dud? What stupid thing am I missing?

[sszeliski]

Help needed.
I ordered a new AcDelco ECM(explained below) and it won't connect to a scan tool, hptuners, or turn on the "powertrain relay". It's behaving as if its not getting power, but the old ECM behaves as if it is, and turns on the relay, hooks up to vcmscanner etc.
Why cant I connect to this new ECM?
More info:
I am performing an engine swap and i have the engine, 6mt, ecu, wiring, etc from a 2014 Camaro V6. The ECM is an E39A.
After scouring the alldata wiring diagrams, i have powered everything that gets power from the factory, in the way that its powered from the factory. I flashed away vats and clutch interlock etc.
The ecm works great and will run the engine, but not well, and it throws code p1682, which boils down to a faulty ignition switch, or bad ecu. Thats why i replaced the ecu. P1682 could be coming from another issue entirely, but for now i am trying to use a new ECM to rule out that possibility. It is brand new from an ebay seller, an authentic ACDelco part number 12653998. Identical to the used camaro ecm.
Why cant I connect to this new ECM?

[07GTS]

brand new ecu may need to be flashed by dealer first then hpt can connect to it, if its blank hpt wont connect