The pressure control switch will be right at the steel pressure tank.
Sometimes when you engage it, you have to hold it on the "on" position
manually, until enough water pressure has developed from the pump to put it
into automatic operation.

It is entirely possible that the pump needs to run long enough to push the
air back though the supply pipe, before it can start pumping water again.
On my vacation house system (after it is off for a few months) this takes
a few minutes to accomplish. While it is blowing air out of the line, I
have to hold the pressure switch manually, until it starts pumping water.

Good Luck

James