Just a few more thoughts to add, FWIW

1. Fresh gasoline in tank? Obvious, but subtle...
2a. If there is a fuel pump, does it pump? (Pull of the line, pull the starter, see if it squirts...)
2b. Fuel pump or not, is there "gunk" or any restrictions in the fuel line?
2c. If there is a shutoff valve in the tank, is it full of "gunk" and does it open to allow fuel to flow well?