Chosen Solution
I completed a rear case replacement,, seemingly without a hitch. But now the phone won’t power up. Either that or the display isn’t working now. I checked the battery cable and display cable and they’re plugged into their sockets correctly. Curious what else I should check. I did accidentally re-connect the battery to the logic board at one point before completing the assembly. I quickly disconnected it after realizing I had a few more steps before I was supposed to plug it in, but I wonder if I could have fried the logic board by jumping the gun.