[ShrimpBurrito]

Take a look at the backside of the water heater switch to make sure there are 3 wires attached to it. You can do that easiest with either a mirror, or just unscrew the 2 screws mounting the switch to the panel and gently pull it towards you. Those wires have blade connectors on them, and they can sometimes pull off if tugged, which someone may have done inadvertently while working under the sink. If some of those wires aren’t connected, that could explain the issue.

Dave