Thank you! I got it sorted:
My spigot has a white tube in the center that is flush with the front of the threads. It appears the screen inside the Pixie interfered with this, and the water did not turn on.
When I checked it against another spigot without that tube, it worked with no issues.
The solve was to pull out the washer with the screen and turn it over, so the screen faces into the Pixie and not out, thus not interfering with the tube in the spigot. A nice alternative for Netro to consider is adding a washer without the screen to the package.