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Hi my name is Robert......
IF the water in the tank is hot and you verified the bypass valve then it could be a check valve issue. Many times on the back of the water heater where the line hooks up they will install a check valve, the check valve will be plastic or brass and have tiny arrows on it for direction of flow, below is a picture. IF you see that I might pull it out and see if you get hot water. It could have been installed backwards OR the spring and disc can fall out and block the flow of hot water. On the valves for the bypass many set ups will have three valves, a hot cold and bypass. The hot and cold should be open (valve handle running with the pipe) and the bypass closed or valve handle running against the pipe.
IF you have an outdoor sprayer make sure the valves are shut, I have seen the hot water do strange things when the outside valves are opened up so make sure they are shut.
To me it sounds like the check valve... IF you have more questions or concerns please feel free to contact me... IF you are satisfied with my efforts please feel free to select a rating, it is the only way I get credit, also follow ups are included.... Robert
Are you on pump or city water? What is this installed in?