My generac 2000 won't start - Generac Electrical Supplies

Along with Barts suggestion..you can open the spark plug access cover and remove the plug and check if its wet with signs of any fuel and a smell of good gas(not stale)..showing that fuel is getting thru the carb. Check for a good spark at this time too by grounding the plug and trying to start it.
GAS TEST: Do this safely- Dip a clean pencil 1" into the gas in the tank and go outside immediately..and art arms length ..light the dipped end of the pencil with a lighter...if the pencil tip does not pop into a little flame your gas could be old or contaminated-drain it and get fresh.
For seasonal engines consider gas without ethanol if available...or use gas treatment which stabilizes the fuel for the unused periods of time and can slow down the gumming effects of stagnant gas.

If it has been sitting for awhile since last used, this is a common problem. The fuel has sat and gummed up and clogged the fuel passage ways through your carburetor.
One trick to clear the passages is to try to get fuel into the generator when starting by spraying carburetor cleaner or starting fluid into the air intake of the generator. Sometimes if you can the the motor to run it will suck on the fuel line hard enough to clear out the gummed up fuel stuck in the lines. Caution: if you use starting fluid, just give it small puffs from the can. Too much can blow up the engine or flood the spark plug.