this is why your Vokéra Easi heat plus boiler is in the error state A01 with a solid red light. There are many reasons for an A01 error so always good to check that the pressure is fine (around 2-2.5 bar)
in my case the boiler shut it's self off because of the backup of waste water from the condenser element.
I'm not an engineer so please phone your engineer before changing anything drastically on your boiler.