Why won’t my iPhone charge after replacing battery and charging port?

My iPhone 5s showed no signs of life until I put in a new battery and it turned on. I tried plugging it in to the charging port but it wouldn’t charge, I replaced the port but it was after the battery had died so it is on the red battery screen. I tried plugging it in and leaving it for an hour but it still wouldn’t charge. The blank screen only shows a blinking red battery and a charger at the bottom even when it is plugged in. I have gone back a few times to make sure I have not broken anything and everything looks fine. The only other thing I think it could be is the motherboard which I have read could cause charging issues but would appreciate any help to figure out my issue.