I bought a used replacement regulator on EBay. The gauge for tank pressure doesn't work, but because the one for keg pressure works I can still use it. I successfully carbonated and served from one keg a few weeks ago. However now I have two kegs hooked up to it with the gates open for both gas lines to carbonate two kegs. I have full tank I just exchanged yesterday. Last night the pressure to the kegs stayed at 20 psi for at least 6 hours. This morning it is at zero and I can't get it to go up again. Needle won't move. The tank and regulator are in the fridge with the kegs this didn't seem to be a problem when I used it with one keg.
Okay, after more investigation, it appears I have a leaky keg, probably. The tank is definitely empty now and it was full yesterday afternoon, so I must have leaked it all out over night. I will have to get new O rings put in, check for leaks and get yet another full tank. I'll learn to always check for leaks!!– Gordon123Feb 3, 2016 at 15:22
Yep, we've all been there. Starsan in a spray bottle helps to find keg leaks. If you hear any gas when you rotate or rock an attached ball lock, the oring can't be trusted.– Evil ZymurgistFeb 3, 2016 at 16:31
Was there any keg lube used? I have had many issues with my kegs not holding pressure when keg lube wasn't used. It helps to lubricate the seals and make a stronger seal than it would using just the seals themselves.
It's cheap and the tube will last a long time. If you are unable to find keg specific lube, any silicone based food grade lubricant will work just fine.
Check for leaks, replace all the o-rings and maybe even the valves. Also get yourself some keg lube and make sure to hit the kegs with high enough pressure to seat the keg lids.