Welcome to the forum
"Sat long enough"...................
Gasoline, the fuel part of it, evaporates and will no longer burn very well if it "sat long enough", gas tanks are not sealed like gas cans, so doesn't take all that long for it to start "going bad"
It also turns to a varnish in the fuel lines and fuel injectors.
How much fuel was in the tank?
You may want to drain it out, siphon it out, and add some "fresh gas", AND some Seafoam or similar injector cleaner to the new gas.
I would change fuel filter as well, $10