What would you have to do to determine it was the solenoid? Get out the multimeter i presume?
That is the easiest way.
You measure across the solenoid/water valve when it should be opening.
If you see 120 volts and there is still no water then:
1. Check that the water supply to the unit is OK.
2. Pull the water valve and check /clean the screen filter on the valve's input.
If both the above are OK replace the valve.
If thetre is no voltage across the valve then often it is a problem with the over fill float or switch.
You did not mention a filter screen in the valve's input side.
If yours did not have one then odds are someone has removed it. I would replace the valve. The screen is there to keep crud out of the valve which could hold it open and cause a flood.