If you got a pressure switch with a little brass lever on the side, you have to hold that lever up until the pressure gets above 30. If you have a standard pressure switch, all you can do is make sure you have the correct voltage leaving the pressure switch. Motors have an automatic overload in them. They usually cool down in about 5 minutes and try to start again. If that is happening, you can see the lights dim or use an ampmeter to see the amps the motor is pulling. If it is trying to start every few minutes but can't, you will need a new motor. I hope the plumber didn't turn the pressure switch higher than the pump can build, or that would have burned up the pump in short order.