Water well will not stay primed. This is a new pump (old house). We can not find any place where the air may be in the lines. We have cattle and need advise ASAP. Things only break at our house on a weekend!!!

 

If your pump will not stay primed, then you have a problem with the check valve or you have an air leak around threads on the suction (well) side of your pump.
Is there pipe dope or teflon tape around all threaded fittings, including the priming plug on top of the pump head? Teflon tape needs to be replaced (clockwise only on all male threads) every time that you open and close that plug and other fittings.
Either rust, sand, debris at the seal or a faulty internal spring is the likely culprit with the check valve. SOMETHING is not allowing it to seal and the water is flowing back to the well from the pump when the pump cuts off.
You can try tapping on the check valve while the pump is running to see if that dislodges anything.
Was the check valve replaced when the pump was replaced?
You probably will have to either remove and clean it out OR replace the check valve, if you don't have an air leak.
My guess is the check valve needs to be replaced.
Good Luck!