Pull the lever wide open and peck on the top of the pump then try it. May be a stuck metering valve.
If that doesn't work clean around the pump top cover and then remove the top cover and see if the metering valve is moving. Turning when the throttle is moved. If it is stuck in one position try moving it left to right to free it up.
If you get it moving and running never shut the engine down with the throttle but rather put the transmission in 10th gear and with the brakes held release the inching pedal to choke it down. This way the metering valve will not be moved to closed position and next time you try to start it you'll have fuel going to the injectors.
Roosamaster pumps don't like to sit up for long periods with the metering valve closed.