When you suspect that the main heater is not working anymore, there are a couple of steps to take into account:
1° Check if the display on the heater is out. The heater is located probably located in the basement
2° Display
A) Display on - The main heater is still working. There might be an error code displayed. Please send a picture of the error code and submit a ticket with the picture through the Help Center.
B) Display out - Try to reset the heater. If that doesn't work, you might need to check the electricity board in the basement.
3° Electricity Board
The electricity board is located in the basement. If some of the fuses are down, you will need to lift them up.
Normally the display on the main heater will activate again and the heater will restart. If this is not the case, please read how to reset the heater.
How to reset the heater
Check this video (from 4'28" ) on how to reset the heater.
In case this doesn't work. Please make a ticket on the help center.