If there is a high spot in the suction pipe you could have an air bubble that is preventing water from getting to the pump. A suction pipe should slope either always upward toward the pump so the air will get through the pump, or always downward toward the pump so the bubble will get out of the inlet.
If it is necessary to have a high point in the suction line, then you must take extraordinary steps to get the pipe FULL of water. Any residual bubble will restrict the flow.
One way to get a bubble out is to connect a wet-dry shop-vac at the pump end until you get all of the air out and a solid flow of water.