Possibly the fuel pump or gas filter could be clogged from dirt or GUNK in the old gas from being idle for so long..
Did ya add some DRY GAS into the tank?
See if ya can test WHAT is in the tank. Possibly a lot of condensate from heating and cooling on summer days and nights then winter. I'd drain the tank.
THEN, put a few gallons of gas into it and add a bottle of DRY GAS to absorb any moisture in left over.
Ya might even try DRY GAS in the tank ya got now.
Just my two cents. I've had moisture get into gas before from the tank being too low and frost forming on the inside of the tank only to melt and get added to the fuel..
ALSO, is the gas filter clogged????? Could well be and maybe changing it would help...
Just a couple simple things that could help...