None of the rooms in the house need heat, all of the heating zones in the app are blue, but the boiler is still firing unnecessarily.
Some combination boilers (made by companies such as Vaillant and Worcester Bosch) have a setting that keeps hot water ready in the boiler for the taps. These boilers can have two programmes built into the front of the boiler: one for heating and one for hot water.
The heating programme needs to be left on 24/7, as the heating is controlled by the Genius Hub system via the thermostat terminals on the boiler. However, if the hot water timer is left on, the boiler will come on intermittently during the day, because a thermostat in the small hot water store inside the boiler (sometimes called a "keep-hot" or "pre-heat" feature) triggers the boiler to heat more water. When the hot water timer is turned off, the boiler will stop turning on intermittently to heat this water, but it will still provide hot water on demand.
Many boilers also have a pump overrun: the pump keeps running for a few minutes after the heat demand stops, to remove residual heat from the boiler. This can sound like the boiler is still on.