what gas? disposable or refillable? same gas or have you changed type?
Your not on a grassy knoll are you?
iain
are you sure there is gas in it?
do you have a reg fitted or is it disposable? if you have a reg does it show pressure and is it set to correct flow rate?
if it has a small bore plastic pipe, is it kinked or trapped.
Only ideas as it sounds like lack of gas.
other than that check the gas solenoid (in the welder) or valve (in the torch) depending on model of welder.
easiest check is to disconnect the wire pinch roller, turn on machine, hold torch near your ear and press trigger, you should hear a puff as the gas flows, make sure the wire cant feed unless you want it poking you in the lug.
paul
Grassy knoll?????