#2 clouds (parafin falling out) at 14F. That happens in the tank, pump, fuel line, filter, water separator, injectors. Diesel Kleen, Howes, etc. is inexpensive: a 32 oz bottle will probably treat a 55 gal drum.
You may also have an ice issue.
In hotter, humid climates, you have more moisture in the air. As the tank breathes, moisture builds up inside. In cold temps, the water will condensate and freeze long before #2 diesel will gel. Diesels have a water separator for that reason.
You could have some ice in the pump or the line. There is another additive that will not just keep diesel from gelling, it will also remove water from diesel in an emergency situation. It is not Heet you would add to gasoline (isopropyl alcohol), but specific for diesel engines. Google will find it for you.
I had to use it once in my diesel truck when temps were -36F at night and -20F during the day some years back. My truck had a (plug-in) heater that was supposed to keep the entire fuel aystem warm enough. Somehow something in the fuel system got too cold anyway.
Over winter, the tank of a stored vehicle will rust (diesel, gasoline doesn't matter) if not filled to the very top.
I have a diesel tractor, and excavator (in Idaho, snow country). I use them in summer. By default, they always have #2 diesel in them. Every fall when I put them away, I add an additive (whatever Howes, Cenex, Diesel Kleen is on sale) to the tank and run the engine to make sure treated fuel is everywhere in the system. Then I fill the tanks to the point where the lid (on the equipment the lid is on the top of the tank, not the side) dips into the fuel when closed. One winter I forgot to fill the tank all the way to the top and left a couple inches of air. In spring, there was an icicle on the inside of the fuel cap... it was rust though.
Push your machine in the garage, if you have one. After some hours, when you get it to start, pour Diesel Kleen, Howes, etc. in the tank and go for a drive / let it idle outside.
