Aberrant Mind missing from subclass selection in 5.5

I am currently running a campaign with content sharing on and one of my players is trying to select Aberrant Mind as their subclass while playing with the 5.5 version of Sorcerer not 5e rules.
I own Tasha's Cauldron of Everything so the subclass should be unlocked but it won't show as an option to be used, it does show when we use the 5e Sorcerer but not the 5.5 version. is there some kind of other book I need to purchase to make this work as I've enabled all content and tried but it still won't display the subclass.

If you're using the 5.5e version of the Sorcerer class, you would need to select the 5.5e version of the subclass instead (which is called "Aberrant Sorcery"). 

If you can't see it, it's because you don't have access to the book that includes it (the 5.5e Player's Handbook). You would need to either purchase that or get someone in the campaign to share it.