Your tank is not full? The tank should fill before anything goes out to the field. There should be two sides to your tank a sludge side and a liquid side. The sludge side should fill and transfer liquid over the baffle to the liquid side and then out to the field.

Is the high point that is spewing before or after the tank? Field that fail usually show water flowing out of the ground. If you are pumping it out of the ground your zone valves may be closed or inoperable