This is a bit of a mystery - I replied to this an hour ago, and now no answer is present, so I'd better start again. The first test is to disconnect the fuel hose at the carburetor end, put a cup under it, turn the whipper snipper so the tank is higher than the open end of the hose, and see if fuel runs out of the hose. If not, remove the fuel tank cap and repeat the test. If no fuel comes out even then, try blowing into the tank. If no fuel comes out when the hose is lower than the tank, you have a blockage in the hose either inside or outside the tank. If fuel only comes out when you remove the tank cap, you have a blocked fuel tank vent.
If fuel runs out even with the cap on the tank, all is well up to the point where fuel goes into the carburetor. Before we go beyond that point, it would be a good idea to check that nothing else has gone wrong. You do that by removing the spark plug, squirting a small amount (a small spoonful) of fuel into the cylinder, and trying to start it. It should start and run for a couple of seconds until it's used up the fuel. If it won't start even when primed in that way, the problem probably isn't fuel.
To illustrate why you need to make that last check, I once knew a guy who rode a motor scooter. One day he tried to start it and failed, despite a long session of kicking the pedal. He happened to live downhill from where we were at the time so he asked me to push him to the top of his street. I did this easily, by applying my right foot to the back of his pillion seat, and riding my own scooter. Before we even got to the top of his street he tried to start his engine, in first gear, which would have dislocated my hip if I hadn't removed my foot very quickly, so I let him coast over the crest and abandoned him to his fate. (He'd taken a drink or two, so it was my own fault for trying to help him get the scooter home.) I later learned that he coasted home, and walked up to the scooter the next morning to try to fix it. He immediately noticed that his first kick of the starter the previous day had neatly dislodged the spark plug lead from the spark plug.
