Is it possible that your disk bursted and the tank is empty? Try to push the pin valve down with your finger. If you can press it down easily, your tank is empty. It will almost be imposible to push a pin valve down with just a finger if it's full. Don't go aiming it towards your eye while doing this. If you have an ASA handy, you can mount that and use that to try and vent some gas in a short fast burst just to see if the pin valve works.