I think if the bypass valve was turned, you'd be getting cold water flowing out of hot and cold tap settings. My understanding is that there is s check valve on the hot water tank outlet that feeds the hot water lines. There purpose is to allow the hot water to flow out but not back in. These can fail and block water flow in either direction. Depending on your Pinnacle model, it may be difficult to access the plumbing side of the hot water tank. As ALJO has asked the model you might get direction from someone with that model that has already tackled this. You may also need the assistance of an RV tech. If your unit is under warranty, contact the dealer or Jayco to see if they will authorize a mobile tech to do the diagnostic and repair.
Dave and Ivy
2020 North Point 315RLTS
Ram 3500/Aisin CC, SB, SRW, Superglide
Firestone Ride-Rite Air bags, TST507 TPMS