The Propane quick disconnect you show in the picture (lower right) is a High Pressure" type fitting, it is designed for propane under around 100 PSI of pressure (more or less depending on weather conditions).
It appears you have installed it on the LOW PRESSURE manifold. That is 11" of water pressure or about 1/2 PSI, not nearly enough to feed a high pressure grill.
(High pressure grills are ones designed to be fed by a disposable bottle or a tank with adapter hose)
If this is a trailer get a Marshall Brass "Extend-a-flow"
If it's a motor home,, then go with the Extend-a-Stay
the "Stay-A-While" by, I think Mr Hearer is an equivalent product to the Extend-a-flow from what I understand.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times