So the first dial (the one which shows the pressure in the cylinder) is showing the pressure but the second dial, which shows the out pressure isn't working?
I can see 2 things that you yourself can check. If not, repair is always an option.
1. This has happened with me many a times to tell you the truth. And it happens all the times when there is NO gas in the tank. Somehow the tank pressure dial keeps showing that there is some pressure in the tank but actually there's is not. So check that first.
2. Second thing that I could have happen is a blockage in the reg. Have you opened the reg recently?
Even a very small particle can cause the blockage in the reg. Remember there was a cap on the CGA valve when you bough the reg? That was just to ensure that no foreign particle can enter the reg. Thats why I always suggest cleaning the mouth of the cylinder before putting on the reg. Any dirt on the cylinder mouth can easily enter reg.
So check for the first thing first. Then to take care of the second thing- try to blow some air from a vacuum cleaner in the opposite direction of the normal CO2 flow in the reg. If it works out, great or go to the repair shop
