Correction: Let me change my comment. I forgot that this is a new tractor. If you've ruled out a clogged filter (from bad fuel you added), and I think you have, get your dealer to fix it. Use the warranty that you already paid for. It is probably a simple problem, but maybe not. If this problem requires serious work, you don't want to be accused of causing it by your continued trouble shooting.
Ignore this: Next, I'd be inclined to disconnect the fuel hose (from the tank) at the lift pump and see if it will gravity-drain with good flow rate. One owner reported crud at the bottom of his fuel tank that blocked fuel flow out of the tank. If the flow is good you can just let it drain into your container, assuming you want to replace the fuel. If the tank drain isn't plugged check the lift pump. It should deliver fuel to the filter at a couple PSI. This is a very simple (and not expensive) pump with a diaphragm, a spring, and a couple check valves. A cam in the engine compresses the diaphragm against the spring (which sucks fuel into the chamber) and releases it (which allows the spring push fuel out). Common failure modes include a leaky diaphragm and sticky/leaky check valves (caused by dirt or gum). If you find a leaking diaphragm check for Diesel fuel in the motor oil.
