With controllers with software version 2.43 and newer the DIY instructions doesn't work.
You don't need to take the controller of the wall, so make sure that the controller is out of install mode and put it back on the wall.
On the main menu (where you see the house)
- Go into menu by clicking on the right arrow
- Scroll down using the down arrow and select filter details
- Screen will show xx% filter life remaining but reset is greyed out
- Press the up and down arrow at the same time
- Reset now option will be highlighted, if not use the arrow up button to highlight
- Press the right arrow and confirm the reset by clicking right hand arrow again.
- You will now see your filter life is 100%.