mine didnt charge at first aswell mb try reconnecting the battery

took me 5 tries of reconnecting

my phone battery started getting worse and worse and didnt display % so i decided to try my luck on replacing it. some small tips from me:

-things u need(from ifixit store): the battery replacement, adhesive strips for battery and back, the iOpener kit and a torx t3 4mm precision bit which is sold separately...

-hardest things when repairing: battery was very hard to get out... i had a friend help me and gently nudged some plectrums under it to make it easier... other hard thing was reconnecting the battery for me... i reconnected it 5 times and on the last try i finally got it right and the phone worked again. that little connector can be tough but still try to be gentle.