Did BOTH of the solenoids 'click' when the ground path was completed (window switch 'ON')? You tested them for power, but did you try the following... arm system as normal with all your wires/lines/bottle hooked up, remove nozzle and tape/plug the hole closed in the inlet tube, start car and rev to 'ON' rpm, point nozzle away from anything you don't want frozen, and hit the WOT switch w/ yo' finger to see if the nozzle is blasting a fine mist or what have you... see what happens in other words.
Sorry if I couldn't be of any real help... just a suggestion. I can't think of anything else. Maybe send your solenoids back to "mustang works" ...you meant nitrous works?
Not sure what their policy is, but NX claims a lifetime warranty on all of their 'noids.... I would imagine some of the other nitrous co.'s do the same.
Let us know what you find out...