I did have the bypass closed while it was winterized. I opened it up and filled the tank before turning it on. I guess air came out as it was filled. The reason I know it was filled was 1) I shut the low point drains as the water came on because it was spewing out. , 2) pushing the relief valve had hot water coming out.
Could there be a check valve on the tank that is stuck? With the bypass closed, I get cold water out the hot tap.
There is only 1 bypass valve on my MH. Another 5th wheel we had did have 3 valves that had to be flipped, 2 (1 on both sides of the hot water tank) and 1 on the line that was to be inserted in the RV antifreeze bottle.