It is almost certainly a gummed up carb...the fuel we buy these days is not good with small engines.
If you are willing to try this, it might get that genset running again:
Buy a spray can of 'starting fluid'...its available at any automotive parts store like autozone, carquest, or the auto section at walmart. Also, buy a can of Seafoam.
Pour some fresh gasoline and an ounce or two of seafoam into the fuel tank.
Open the air filter housing...usually it is a couple of metal clips or plastic latches, or some gensets have a cover that is held on by one or two screws.
Pull out the foam filter. You should be able to see the round opening into the carburetor.
Make sure the choke lever is OFF. Turn the generator on-off switch to ON or RUN.
Spray some of the ether (starting fluid) for about one second into the carb opening, quickly move the choke lever to CHOKE, then immediately pull the starting handle normally, and briskly.
You might have to repeat this a few times, but when it 'catches' it will run on the ether for a few seconds then stop.
After doing this a few times, letting it run a bit, sometimes the higher vacuum produced during this procedure will pull fuel right past the carb needle and/or the carb jet and the genset will run normally...if NOT..then its a sure sign the carb is plugged up.
If you cannot get the genset to run with the starting fluid at all, then the ignition system is suspect, maybe a bad spark plug wire or boot, or a loose or fouled plug.