2015 DS3 1.6 Diesel - Blower only working on number 5 not heating up

[shabbaranks]

Hi,
As the subject describes my girlfriends mum has a DS3 and it recently stopped blowing hot air (the car not the girlfriend) it blows on number 5 but not 1-4 also the air is cold and I read it could be the resistor pack?
I followed a YouTube video understanding that the resistor is under the passengers footwell but I couldn't find it - any ideas\suggestions please?

Thanks