iPad 9th gen doesn't charge even after port and battery replacement

My iPad 9th gen started charging very slowly (no difference between Apple charger or 3rd party). It could take 15+hrs to get from 30% to 80%. At the same time it started draining very quickly, I would get a few hours of normal use such as Facebook, email, browsing the internet or just reading downloaded books. I had the battery and the charging port replaced, but there's no difference. At this point I have to be tethered to the charger to be able to use it. iPad is only 3 years old. Any suggestions on what to do from here?