help asap: swapped valve body/tcm, now car won't start

[thebeast]

First, I did not disconnect the battery.
I dropped the pan, unbolted valve body, removed tcm from valve body and installed a tcm I knew worked in my car from the other 3 6l80s that burned up.

Go to start the car, it won't start, or even turn over.
Almost as of the ecm is locked out.
hptuners won't even scan, load tune, and there is a dtc. But I can see what it is or even clear it with my aero force gauges or scanner.

What should I do?

[TooManyHobbies]

Have you tried disconnecting the battery for a bit?