Screen flashes on for a second then off after repair

I recently got 2 galaxy s4’s both working fine but one had a damaged screen the other one didn’t as the one with the good screen any way I decided to swap the motherboard from one phone to the other and with a bit of experience with repairing phones I’m pretty sure I did not break anything but when I tried turning the both on after the swap they both just flash on and then straight off again I swapped them back and they worked fine also they are both different model numbers any idea if I swap over every component rather than just the motherboard if that might work