My pump (2 wire) does not bring up any new water and I have already replaced the pressure switch what else could be wrong? It appears that the voltage is OK but I.m not sure how to check

The air dissolves into the water and the volume of air acting against the water diminishes to the point it no longer does its job and the pump comes on very frequently, up to the point there is no air remaining in the pressure tank at all. I've seen that situation before.