Replaced E40 with new one, ecm can not connect anymore

[Tapi]

What did I do wrong:

2005 Corvette had faulty ECM (throttle sensor line was supplying voltage). I read entire (ECM & TCM) and purchased license.
I put in a new ECM which was programmed to Trailblazer earlier with Efilive.
I read entire (ECM &TCM) and purchased license.
I wrote entire (ECM & TCM). This didn't show any errors in writing.

Now the car won't start and I'm unable to read ECM anymore, neither is writing to ECM possible.

Scanner shows CAN bus errors.

Did I brick this and how to continue?

EDIT: Just learned that whilst HPtuners isn't writing everything according to VIN, I need to flash the ECM as Corvette before anything. I assume I didn't do anything that cant be reversed by flashing this to stock with Tech2 or MDI.