No propane from second tank

Success!
Opened valve slowly, heard the click and off to the races.
thx

RV is 2006 HR Savoy 5th wheel.
Going out to trailer Wed - Sun, will check operation then.
thx much

That device (Red Regulator) is a single stage 30# regulator.
Takes high cylinder pressure and reduces it to 30# before it goes across front of 5vr to 2 stage regulator which feeds propane system.

Don't know what RV or age of RV but those red regulators were a problem going bad.

And yes if you open cylinder service valve to quickly you can trip an excess flow device in the big acme nut that connects hose to cylinder (OPD is a Overfill Protection Device that stops filling of cylinder at 80% liquid level)
The excess flow device (ball bearing inside nut) moves towards hose when you first open valve and then moves back to center position when pressure downstream equalizes. If opened to quickly it doesn't move back to center.
Close valve....then slowly open (sometimes you can hear it click) then open valve fully

IF it still doesn't flow....then it probably is that Red Regulator.

Thanks very much...
Finally got savvy with posting pics as a bonus today

Nope just close it and reopen very slowly. I have one tank on the 5th wheel which is very finicky.

Didn't do it slow...
Do I try again slowly, or does this OPD have to be reset? If so, how do I do that?

did you open the second tank valve SLOWLY. If not you may have triggered the OPD valve and you will barely get any flow.