This thread should have some useful information:
https://gbatemp.net/threads/new-3ds-xl-fuse.416208/
I haven't read the whole thing thoroughly, but I think that people in there had some success in fixing that issue (if I recall correctly, it...
My problem started after putting the battery in backwards (positive pole with the negative). I had the console disassembled because I was trying to fix another problem and accidentally put the battery in the wrong polarity and then it wouldn't...