As mentioned call HWH. You will require patience and persistence as they are probably swamped after a holiday weekend. If you need to take it someplace you can relieve the pressure by following the directions in your manual and turning the "t" handle valves and cranking it in. Sounds like the infamous "shuttle valve" to me. A new one is not that expensive and easy to replace. Good luck and keep us posted.
Tom, Cheryl & Blossom(coonhound mix) Formerly of Bellingham,WA'05 Winnebago Journey 36G. FL-XC, Cat 350, aero muffler, AFE filter, 4 FSD Koni's, ultra track bell, SafeT+, FMCA397030, WIT 129107