had this happen on my 2002 Forester - of course it happened in the dead of winter, too..
in my case, it was a bad case of rust in the small hose connections attached to the filler neck.. as in rusted completely shut so vapors could not move around. I would not expect that in Colorado, but i suppose anything is possible. there is also a small "switch" thing attached to the filler neck, up fairly high, that can be purchased separately.. called a "fuel shutoff solenoid"
for me, replacing the entire filler neck, including the above mentioned solenoid, was the answer/cure. The replacement filler neck i purchased came with the solenoid already on it.
fwiw, i do have a cel for the evap canister solenoid located at the charcoal canister and the car runs fine, and takes fuel fine, so i do not believe that particular unit has anything to do with fueling.. I do have a new one here, but getting to the old one, and getting it off.. yeah.. major rust monster involved, which is why it has not been done.