Battery does not charge after change

David, of course you want to double check your work first. After that replace the new battery and see if the old will charge. It is possible that you have a bad battery. The standard way to check will be trying to charge with a different charger (use a wall charger not your computer to ensure a higher amperage) and make sure that you have a known-good cable. Check the dock connector for any broken bend or corroded pins. Clean it with some isopropyl alcohol and a few puffs of compressed air. If all that should fail, you will have to check the charging circuitry on the board. There is always a possibility of pry damage to some small component.