If no central heating in the property.
Make sure that the boiler is set to this mode and press on OVERRIDE
Please ask guest to set the thermostat to 27
If all will not work please ask the guest to go to the kitchen area and make the following adjustments:
If the Burner on is blinking they will need to turn the red knob to 0 till they hear a click for 5 seconds then move it to middle/half way till you see the burner on stays lit then turn it to the max until they see the led lights stays on
Just follow step 1, 2 and 3 and keep an eye on the Burner On indicator.
The sample video below is what they should hear and is not a how to fix video.
https://www.youtube.com/watch?v=wwdbHoGAK9g