Why is there a "ground" and a "solenoid supply ground"? Aren't they the same thing?
Just so you know, I have tried switching around wires connected to Drain/Source pins just to see if anything would happen but.......nothing.
The Arduino digital pin should be connected to the Base of the transistor. Does the Arduino's ground need to be connected to anything then?
So, what happens if you touch/connect the 1K resistor to arduino's +5 (instead of a digital output)?
Take a look at the gate threshold voltage in the datasheet, this gives a good clue to their suitability for low voltage use.