Carol and Kevin,

It's doubtful that it is the thermocouple for the hot water heater.  If you have a pilot light, you have a working thermocoupler.  Its design is to shut off the gas to the pilot if it fails.  The way it works is that as long as it gets heat from the pilot, the pilot stays lit.  If the thermocouple goes, so does the pilot.

I would suspect either blocked lines or the thermostat control.  Since you have had hot water in the past, it is obvious that your winterizing bypass valve is in the proper position to allow hot water to flow.  That is, unless someone has shut that valve off.

Terry