You said "Cycled the bypass valve" Not Valves like I have but Valve .. singular.
This leads me to ASSUME you have a single valve bypass system. If the assumption is wrong you may go to the next reply now.
Single valve systems are not really single valve. There is one 3-way MANUAL valve in the COLD water line to the heater and a CHECK VALVE at the hot water outlet (may be one on the cold inlet as well but that's .. No readon for it)
The check valve can "lime up" or crud up if you like, and not open thus not allowing hot water out of the tank into the plumbing.
If possible remove it (it just screws in) and replace it or better yet replace it with a quarter turn valve. If you can not remove it .. Gut it (needle nose pliars and pull out whatever is inside it) be sure to label things so that anyone Winterizing knwos that vave is different now.