Thanks for your suggestions Old-Biscuit, greatly appreciated.
Right now the fridge is near empty. It was giving the E-1 when it was loaded as well and had a small circulating fan operating inside.
I cleaned all the ground and solenoid connections. Also tested the Thermistor with the sensor in a glass of ice water. It tested at 8490 Ohms so I assume it is still working properly.
After I finished and re-started the fridge on electricity, it gave the flashing E-1 within half an hour.
Not sure what to do next, the propane pressure regulator or the fridge propane valve and solenoid.