The latest champions dropped 3 places this week with their song Dimelo, charting at Number 9 in the Christmas No. 1 chart.
Instead, the Official Christmas Number 1 2017 went to Ed Sheeran with his song Perfect which stayed at Number 1 for a third week.
Ed told Officialcharts.com: “Thank you very much for making Perfect Christmas Number 1.
"This is an actual dream come true and I’m very proud and happy. Thank you so much and have a very Merry Christmas, happy holidays and a Happy New Year.”
Ed beat none other than himself from getting to Number 1, with his duet with Eminem in second place.
Wham’s Last Christmas completes the festive top three a year on from George Michael's death.
As for X Factor 2017 champions Rak-Su, Dimelo was their winner's song, a duet featuring rapper Wyclef Jean and producer Naughty Boy on the group's own original song.
The track peaked at Number 2 earlier this month behind Ed's Perfect, just missing out on the top spot.
Rak-Su missing out on Christmas Number One is not too surprising given that the final this year took place earlier than usual.
It's now been three years since the last X Factor Christmas Number 1 when Ben Haenow had the festive char topper in 2014.
Following their victory, Rak-Su have been signed by Simon Cowell's Syco record label and begun work on their debut album.
Runner up Grace Davies has also been offered a record deal after finishing behind the boys in the final earlier this month.