I replaced the well pump ,pressure tank ,pressure switch and check valve.
The switch will not kick on at 28 .at go's to zero.is there anything else to look
For that will make the pressure switch kick on.

Are you sure you have power to the control box> are the contacts in the closed position? What's the bladder tank charged at? Back to you, Tom

Agree with Speedball. Make sure your breaker is on. If it is, then remove the grey cover from the switch (with the power off) and look at the four sets of points. They should be closed (touching). If they are closed, then use a voltmeter to make sure you have power at the leads which go to the pump. When you put your contacts on the two wires going to the pump (red on one, black on the other) you should read 240 volts.

How old is the switch? I ask because switch points can become pitted to the point where they will not conduct. With the power off, you can inspect your points. If they appear pitted, then use an emory board to give each set of points a couple of strokes. That should get the switch back to being workable, but I'd replace it at some time afterward. Switches are cheap and easy to replace.