Fading power light that lasts 0.5sec (no cfw installed)

I recently bought a replacement motherboard directly from ifixit to swap into my new 3dsxl. theres no connection issues as ive ruled out the hardware problem (light for a few sec, then pop), but ive been getting a new light. on power on it turns on for about a sec then fades off and doesnt boot. it doesnt abruptly shut off, it just straight up doesnt boot. maybe software related?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0

crwdns2944067:02crwdne2944067:0:

Assuming you've checked all the ribblon cables, see if safe mode does anything. Using the 3DS's Safe Mode

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

I think this worked?! I booted into safe mode, lights came on like it was working but there was no display. inserted sd card again and it booted up no prob. Thank you!

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

crwdns2934285:0crwdne2934285:0