Welcome Djnole79. I hope you enjoy your vintage Argosy, both traveling and working on it. It seems like there is always some problem to solve. Part of the fun for me.
I think I would start following the path of the city water starting at the connection hose. Look for reasons that would block the city water pressure and flow. There may be a pressure regulator, or a "one way valve", or a shut off valve, or a filter right close to the city water inlet. Any of these components could block city water. Once you know they are all good, then follow the line to the next component. If all three shut off valves at the water heater bypass are closed, it could block city water pressure depending on how the water heater is plumbed in. Most water heaters are fed from the "main" line, so it is likely some cold faucets would work.
A plumbing system is just pipes and valves. Just follow the city water along its pipe and try to figure out what could be blocking it. Once you get the city water pressure and flow working, you can test the fresh water tank and pump.