Meta Data (inserting the primiary category?)

Is there anyway to add a categories primary category into the meta data.

I am using the Yoast Seo plugin and on this page it says I can insert the below snippet variables to the yoast seo meta templates. But it isnt working on your template..

https://kb.yoast.com/kb/yoast-wordpress-seo-titles-metas-template-variables/

Primary category %%primary_category%%
Category %%category%%

Let me give you an example. The page below is the category ‘Dior’, it is within the ‘Watches’ primary category. Im trying to insert the word ‘Watches’ after the category name within the page title and meta description.

https://www.hushhush.com/watches/dior/

But the %%primary_category%% snippet isnt working? So I cant pull in the main category name?

Help!