When you overdischarge the cells (most speed controls will do this) it hurts the cell and can cause it to false peak.

Try charging at a very low current (like 1 amp) for about a half hour to an hour. Restart the charger if it false peaks but maks sure the cells don't get hot to the touch. Let the pack set overnight to allow the chemical process in the cell to restart and stabilize. Then you should be able to charge the cell completely and it will take a charge.

The first cycle after you do this won't be very good but the pack should be fine after that.