Thanks everyone. I learned a little since beginning this thread.
It seems that the lack of LP flow is the result of the LP leak detector and safety shut off solenoid valve. It's the discontinued CCI Controls LP Gas Detector Alarm, model 7719: https://www.safehomeproducts.com/shp...19/7719_l.html
The solenoid is electrically in series with the alarm module.
I read on the internet that the shut off valve scheme from the detector alarm is no longer needed due to safety standards changes. Modern RVs do not come equipped with the solenoid valve.
I removed the valve and gas now flows. I'm going to replace the alarm panel with a simple audible type.