Whats the minimum discharge for a 12v LiFePO4 Battery?
Opinions on maximum discharge vary, but I would not discharge beyond 2.8V per cell (as always, it's a capacity/cycle life trade-off, but LiFePO4 batteries have a very flat discharge curve at about 3.2V per cell and will only start dropping just before they are empty).
At 2.5V per cell, they are definitely empty; at 2V per cell or below, they may be damaged. There are 4 cells in your battery, BTW.
Even though it may be recoverable, I would return it as a DOA.