Tank heaters no longer showing

I suspect something has gone astray with your Advanced Settings.  The latter can be accessed by holding down the settings button until Advanced Settings appear.  In the early days I had a problem like this which was only resolved by the dealer with a software update.

Just checked my Advanced Settings.  As I thought there is a toggle switch for the tank heaters on the first page.  If its changed without you going into Advanced Settings, it suggests an underlying problem.  My Advanced Settings had a mind of their own and kept changing until I had the software update.