Tubular electric heater. Failure of the heating element is a very common cause of breakdowns. If this is exactly what happened with your water heater, then the electric heater will have to be replaced.
The control electronics may burn out if water has leaked directly from the tank to the control circuit.
The heat exchanger can become clogged if the water contains a lot of mineral salts. In electric boilers, scale can accumulate around the heating element, as a result of which, water heating can almost completely stop.
Repair of electric boilers begins with the diagnosis of the device and the determination of breakdown. Most likely, the broken part will need to be replaced. In case of clogging of the heating element with scale, washing the boiler with a special solution will be required.
The main preventive measure may be to protect the boiler from hard water. To do this, it is necessary to install a filter that releases mineral salts from network water. It is impossible to do without regular maintenance, so contact the masters regularly, this will help to avoid sudden breakdowns.