The 14 volts on the battery pack is plenty. I bet if you check the voltage on the top post of the battery it’s less then 1 volt. It’s the computer chip board, it’s not letting enough voltage up to the top post for the charger to recognize a good battery. I’ve revive about 6 batteries so far and still use them now. But I have two right now that read good on the battery pack but won’t let the voltage up to the top of the battery post where it plugs into the charger.
You need to check the voltage of each cell. if you are getting 14V, probably one shorted cell. If you have a lith charge that can charge 1 cell at a time, you might be able to recharge the 1 dead cell. Trying to fix the dead cell with a 14V charge across all the cells won't cure the problem.
Maybe you use too powerful charger to reanimate your battery, it’s giving 3 amp and its to much. Try another charger with less power, like an old style black P118 which can charge Ni-Cd and Li-Ion types of batteries. It gives about 1,4 amp, I use same to my batteries when they won’t charge in another powerful charger
