I installed GasStop but it's not working. The gas won't flow through it.Updated 17 days ago

The most common reason reason is that it has not been primed. After installing GasStop you must pump the valve/propane level indicator to get the gas flowing through it. Give it 5-6 full pumps to start the flow.

Another common reason is simply that the tank is out of propane. 

You may notice that in colder temperatures (approaching 0°C/32°F), GasStop may shut-off more readily when used with higher demand appliances like propane generators, and/or on longer length pipework. For optimum performance during colder temperatures orientate your GasStop so that the gauge is facing the sky.