I just got two tanks exchanged after not having oxygen for 2 years (long story).   I assembled the regulator onto a tank and the O2 is not pumping through the regulator and mask.  I can hear the O2 leaking out of the connection and am seeing 0 presssure on the gauge.

These tanks were newly filled and I do not see any damage to the regulator.   I tried the other tank with the same result so I can only assume there's an issue with the regulator.

I do not have pics of the connecting parts for a standard regulator, should there be a rubber ring between the regulator and the tank where the oxygen is released?   Any other thoughts?

I'm desperate to get this working as I am out of sumatriptan shots and with changes in my insurance I cannot afford refills at this time. 

Any guidance is greatly appreciated!   I think I may have to replace the regulator if I can find one locally today or be forced to order online.

My CGA-870 reg did the same thing and it's clear it was shot.  I bought a new one on Amazon Prime and bingo, i'm back in business.  I will say, it was obvious there was a leak internally because I could feel the O2 escaping.  Sometimes, that little brass and elastomer seal leaks as well. 

Chad