On my 2013 911.1, I have had a couple of opportunities to wonder why the HVAC wasn't blowing any air. After reading this thread on Rennlist, I found an answer.
Both times this happened, the car had sat for a week or more. It turns out the fan can stick. An easy fix is to open the frunk, and remove the air filter box. When the box is open, you can see the fan. Give it a turn, put things back and start up the car. Should be working.
The other reason my AC wasn't working was due to taking a rock at speed through the radiator. Once that was replaced and refilled, I had cold air again.