Screen, display broken on note 20 5g- Read question

New note 20 5g bought April 2021, took a rock to the screen and display, this phone model is sm-n981u1. Bought new screen, display, and frame, switched out the innards from old phone in to new phone, power it on and all I have is a snowy screen, model of replacement is sm-n981. I switch the innards back to old phone and now i have snowy screen as where before the switch i had my display working in old phone. Would this be the motherboard main display flex cable issue, or the motherboard?