What model tractor? Have you pulled the supply line at the tank to verify if will free flow fuel?
Algea and trash will accumulate in the tank and can plug even a 3/8" diameter line.
Not fun but possibly necessary, pull the tank and clean it. Easy method that sounds stupid, buy some small smooth fountain stones, remove the sending unit and fuel supply port, it can have a sock on the end like a strainer, make a tin cover for the sender port, use an old inner tube for a gasket, pipe plug in the supply line dump the stones into the tank, add a gallon of power service and throw the tank in the back of your utv or pick up, drive around, rotate the tank often and drive around some more. The smooth stones will agitate the algea and and dirt/trash loose. When you are satisfied, remove your tin cover and dump the stones out and then rinse out the loose debris. Once the tank is clean, flush the lines to the factory filter, flush the lines up to the injectors as well. Once you have flushed the system and replaced all of the filters/strainers, install a marine fuel filter with water separator and water drain as close to the fuel tank. You can run premium diesel fuel, Cenex is one, don't buy more fuel than you will burn in 30-45 days, our fuels are shit nowadays.
Keep Hot Shot Secrets Diesel Extreme is a great product to keep around and use liberally.