New 3DS XL not booting after lower LCD replacement

The touchscreen on my New 3DS XL broke recently (half the screen turned into a dead zone), so I bought a new LCD and digitizer off the internet and swapped it out. However, when I reassembled everything, the system wouldn’t boot. The blue power light turns on, then after a few seconds, the light goes off and nothing happens.

I thought this might be because I slightly bent one of the black ZIF connectors that you’re not supposed to open. I didn’t force it all the way open, but it’s definitely looser than the ones I didn’t do that to. Other people on here said that bending those just makes them hold the cable more loosely, and I tried booting while holding down the connectors and cables in place, but that didn’t help.

I also thought my replacement parts might be faulty, but putting the old LCD didn’t work either. (The system did boot with my old LCD prior to my repair.)

I still get a charging light when I plug it in, and the battery was full before the repair, so I’m certain it’s not a battery issue. (An empty battery should flash a red light when trying to boot the N3DS, anyway.)

I’ve disassembled and reassembled this thing a dozen times, making sure I’ve reconnected everything correctly, but to no avail. Has anyone else had this problem and found a solution?