Does anyone have any idea what this means?
Thanks!

Thank you!! Somehow I failed to spot that in the manual myself, this is very helpful!chas wrote: ↑Thu Oct 19, 2023 9:07 am From the User's Manual found on this site:
5.3 Steam Boiler Temperature Detection System Failure
(only with the boiler turned on)
This is a blocking alarm and occurs when the temperature probe of the boiler is in short
circuit (temperature >145°C) or it is in open circuit (disconnected) condition (temperature
<60°C). The lights 19-20-21 turn on.
The alarm can be temporarily cleared by turning the boiler off (Press BOILER (26) button.)
Eventually you will need to turn off the VII and request service.