The link you have is different to those now sold via Dyson. They’ve either linked you to the incorrect model or you’ve landed on an out dated page. They retired the model you have last year, they now offer a combined filter, instead of two.

Order through the filter selection on their website instead. You should see a breakdown like this: https://www.dyson.co.uk/air-treatment/purifiers/accessories

Similar experience from the start of this month:

Hi everyone, 

Great news!

I approached the App team advising of the In-App error, and they’ve just confirmed that the link has been fixed!

This is another perfect example of where our community is helping to make Dyson better! 

Thanks to everyone involved. 

Stuart 

Hi the link in app hasn't been updated still sending me to the old filter, wasted a lot of time looking into this. 

Yup. The app is still not updated. Also, the newer filter has been out of stock for weeks as well… and seems to have become 30% more expensive within a month, as the posted screenshot shows £65 and it is currently listed as £85. It's hard to stick with OEM with all these issues.