Hi Dale, this is probably a common blocked canister where the vent hose becomes clogged as well. It should be a simple fix by your mechanic.
Its EPA ORVR - 'Onboard Refueling Vapor Recovery' related , as you pump gasoline into your gas tank it pushes out air thru a vent tube canister filter setup. When the air can't escape due to a clogged line then the nozzle at the fuel pump shuts off.
Those nozzles are highly intelligent, I don't how they know when those canisters are clogged but they do. :)