Phone app can't connect to P85D

For the first time since I took ownership in December, my P85D can't be woken up by my phone. The car is set to "always connected". It's cold here (maybe 15 deg F) but it's been colder before and I connect by phone every day.

Any others have this problem? Could it be a server issue or does the phone app connect straight to the car with no intervention by Tesla? I'm hoping my car hasn't been stolen by a thief sophisticated enough to disable connectivity (highly unlikely based on where it's parked...)

Follow up: it turned out to be a problem with the 3G connection. When I entered the car, everything was fine except I noticed the nav map wasn't updating its graphics and the Internet radio couldn't load the next track either. So the phone was no longer on the Internet despite showing three bars of 3G signal. Somewhat counter intuitively, I fixed the problem by turning off the wifi and turning it back on. (There is no 3G reset option that I could find at least).