DIAGNOSIS The machine is not recognizing the new filter. The filter life counter must be manually reset after a filter change.
FIX Reset the filter life counter using the Dyson Link app. Open the app, select your machine, go to the filter section, and select 'Reset Filter Life'. Confirm the reset. The percentage should return to 100%.
IF THAT DIDN'T WORK Ensure the filter is the correct model (it must be a genuine Dyson HEPA/Carbon Combi Filter for the BP04). Check that the filter is fully and correctly seated by removing and reinstalling it, aligning the arrows on the filter with the unit.
HEADS UP The machine will not automatically detect a new filter. You must perform reset in the app every time. Failure to reset it will cause the machine to incorrectly indicate 0% and may affect performance logic.