When you try to install the AquaClean filter not during first time use, but after having brewed approx. 25 coffees (based on 100ml cups) or more. The machine will indeed request to descale the machine first.This because the machine has to be completely limescale-free before you install the AquaClean filter.
First descale the machine and then install a new AquaClean filter. After descaling, the filter counter is reset to 0/8. Always confirm filter activation in the machine menu. Also do this after filter replacement.