If your old battery was still charging you will need to open the phone back up and check the battery connector is seated properly also check that you haven’t nudged or knocked off any of the small components around the connector. After reseating the battery connector if it still will not charge you will need to try another replacement battery as the one you purchased is probably faulty.
If you’re old battery stopped charging and showing percentage the same as the replacement one you will have a board issue that will require a reputable repairer to diagnose.