Problem: no water, no pressure. Well is aprox. 20 yrs old, pump was replaced aprox. 6 mo. Ago, tank has been replaced, pressure switch has been replaced, kick in is 28 psi, kick out 42 psi. 40 psi in tank 38 on gauge.
Problem does not happen all the time, and does it with no water running. Any answers

40 psi in tank
What does that mean?

If it means that you have pressurized you tank to 40 lbs, that's wrong.
Tank should be pressureized to two pounds less than pump cut in setting (26 in your case). That is with the tank empty.

problem does not happen all the time, and does it with no water running. Any answers

So you are saying that you can, for instance, go to bed and the water is working, but wake up with no pressure at all. Correct?

Is the pump in the well or above ground?

You've done a lot of replacing recently. What caused that?

What does that mean?

If it means that you have pressurized you tank to 40 lbs, thats wrong.
Tank should be pressureized to two pounds less than pump cut in setting (26 in your case). That is with the tank empty.

Tank pressure when empty is 26 psi

So you are saying that you can, for instance, go to bed and the water is working, but wake up with no pressure at all. Correct?

Is the pump in the well or above ground?

You've done a lot of replacing recently. What caused that?

Pump is in well, parts replaced to fix this problem, and yes go to bed with water wake up without water and pressure gauge at 0

Sounds like leaking foot valve? Do you have a pump saver circuitry in pump switch?

Not footvalve, but checkvalve. Still, same basic problem. If the CV is leaking, the pump will cycle ever so often when water is not being used. Is it doing that?

Should be a CV just above the pump in the well. But you can put one between the wellhead and the tank if needed.

HK is looking in the right direction with the switch.