This engine ran fine before when it was put in storage in a building approximately five to six years ago. I’ve found no signs of rodent damage.

Your problem probably is that you used biodiesel blend of fuel.  I had a tractor that sat two years with a B20 blend.  When I went to start it, it would not start.  I drained the fuel and put new filters on the tractor, and the engine still did not start.  The JD mechanic pulled the pump, and I went to a diesel pump repair station, and they reworked the pump and they said this was very common for a Yamar pump.  If the pump sets without being used for a period of several years, the fuel will deteriorate and get sticky, and it will stick the rack in the pump, and you will be unable to get it started.  A lot of the red fuel sold in agricultural equipment, if it is #2 fuel, will be 20% biodiesel blend fuel.

The most common biodiesel blend is B20, which ranges from 6% to 20% biodiesel blended with petroleum diesel. However, B5 (a biodiesel blend of 5% biodiesel, 95% diesel) is also commonly used in fleet vehicles. B20 and lower-level blends can be used in many diesel vehicles without any engine modification.