First, I appreciate you'all taking the time to assist.
The water source is my house hose. Pressure is real good so I use a pressure reducer to 45psi. Like most of us I have been doing this for years. In fact, that is what is most confusing about this. I have changed nothing on the coach or my hook up routine.
On my coach the water service panel is on the drivers side. It is the standard style with fresh tank fill & over flow and pressure hose inlet all under one cover.
This is what I have done:
..I have had this panel completely out.
..I have run water thru the hose fitting.
..I have checked the back flow valve inside the hose fitting. It moves freely.
(This I know since I had this valve completely apart on the bench.)