A I had a Safari DP with Onan propane generator, 6200w on LP,
The 100# frame mounted tanks are set up for liquid delivery, the vaporizer? Is mounted at the generator intake manifold, where the carburetor would have been,
AFAIK LP from 30# cylinders is strictly vapor feed Not LIQUID,
A pressure regulator at the cylinders can Ice Up, from the moisture in the tanks freezing due to the COLD outside ambient temperature and the cold produced by the vaporizing of the LP, the lower the LP volume, the more likely this will happen
Also sometimes in southern states in warmer weather you get LP that is more butane than propane,should not be the problem if you filled the cylinders recently, but if it's been a few months, like summer or early fall? Who knows?
butane will not turn from liquid to vapor at 13°F, as temperature drops below 32°F, the process slows down until it reaches the point where it stops, the generator simply gets no fuel or not enough fuel to stay running, neither will the heater etc..and the regulator does not have to be iced up (frozen), there is simply no fuel vapor to burn