iPhone 7 not detected in recovery/dfu mode?

Hello, I recently bought a 25$ iPhone 7 to restore with a good 128gb motherboard, however I decided that I wanted to do a logic board swap with another iPhone 7 mobo I had bought because it had the original home button with it. After installing the new logic board, I was surprised to see it stuck on the Apple logo and boot-looping, as well as not being detected in recovery mode. So I took that board out and put the old one in just in case I was losing it, and after re-installing it, the old board, too, started doing the same exact thing: Boot looping, and stuck on the apple logo, unable to restore because recovery and DFU modes don’t work since none of my 3 computers can detect the phone when it entered that mode. I have tried a new dock, new cables, multiple computers to no avail. All the screws are in the board in their correct holes so I know i’m not missing any grounding, and I have tried unplugging everything except the bare essentials to see if it was a failing component, but no. I actually tried to re-install the new board as well, and it started working for a while before I unplugged the cable, and plugged it back in, then the phone shut off and started bootlooping. Can anyone help me figure out what on earth is going on here? I feel like I’m losing my mind! Thanks for helping, Ben

Edit: I have replaced the battery with a quality known-working high-capacity aftermarket battery, and have tested the board with the original working Apple battery.