Replaced screen and battery, phone will not boot or be detected.

Hi! iPhone 6 here, broken screen and dying battery. Figured I would fix both at the same time. I replaced the screen and battery and the phone wouldnt power on at all. I tried to insert my old battery (but I bent it pretty bad removing it) and it would power on the screen, to the white apple screen and be stuck in a boot loop (I figure from me basically bending the battery in half removing it.)

So I assume it was a bad battery I ordered, and ordered another one, from amazon again however a different seller. Same problem. Insert battery, no activity from the phone. Cant recognize it on itunes either. Help! Did I really just get two defective batteries in a row? Or is there a bigger problem here.

Thanks