My daughter told me that we had no water. I went into the well room and the psi gauge said 18 psi. I unplugged then plugged back in the well and it fired right up. But once it hit 40 psi (cut in) it shut off immediately and the pressure dropped in seconds. If I unplug it then back in it will usually kick back on but it repeats the same thing. The well pump is brand new as the plumber installed it and the pressure switch last week. The pressure tank is 5 years old and holds air fine. Thoughts on what could cause this?