I guess you don't have enough charging time. Look at the output voltage (V) and current of your charger, and then look at the capacity of the battery. Your battery capacity divided by the output mA of the charger is your charging time.
Excluding the above reasons, you should try to discharge the battery (it may take several hours) and then recharge it. If this doesn't work, the battery will be scrapped.
Even if it was not charged and discharged more than a year ago, the battery should not break down so soon.