I have bought this house from 78 and it has nobö electric panel radiators 400V. I tried to turn them on for the first time but they won't turn on. The interesting thing is they are a bit warm where the temperature gauge is. What could be wrong with them?
Without the manual I can't tell but my guess is the green tab sets the turn on temperature and the red stop is the turn off temperature.
Set the green up to 25°C and see what happens. Set the red where you want it to shut off.