If it's the original battery it's about 13-14 years old and well past its lifespan. If it's a newly purchased battery, contact the seller -- there's no way it's OEM, but they presumably back it with some sort of warranty. Also check setup (F2 at powerup) to verify that the AC adapter is recognized -- if it is not, the battery will not charge.    
BATTEERY IS NOT GETTING CHARGES UNABLE TO IDENTIFY  BATTERY
BATTERY NOT IDENTIFIED