Water Help, CRAZY mystery, Calling all Plumbers.

Thanks all, Here is what I tried/did...

Replaced Screen on City Water Inlet (properly...did it wrong once before, lol).
Replaced Check Valve on the Water Heater.
Wrapped/Skirted RV and put a heater underneath.

EVERYTHING is working again.

It was FROZEN and needed a thaw...I cross checked EVERYTHING above to VERIFY that. THANK YOU to all for your help!! Happy RV'N