How did I brick this computer? $06FF Checksum Failure

2007 GMC Sierra 5.3L, Controller PN 12614088

I was simply doing AFM delete on this truck and when it was done flashing the tune it gave a $06FF Checksum Failure error. Now there is no communication with the ecm, no check engine light with key on. This thing is dead. I've searched for a way to bring it back and tried several things but nothing is working. Does anyone know what I might be able to do to get it back?

I've tried re-flashing it, I've tried a total re-flash, I've tried programing back to factory with Tech2 (Tech2 doesn't see it)

Anyone have any ideas?

Thank you

If Tech2 doesnt see it, its prolly time for a new ECM.
Ive never bricked a E38 but ive had about 7 come in that where dead and need to be replaced before i could program them.