Selecting/Adding custom taxonomies to CPT


I looked at this: CPT: Taxonomy selector in Pro Forms - #2 by div

but I can’t properly manage to create a connection between my select field and the corresponding taxonomy to be applied on a CPT (Metabox).

What is the proper way? (sorry local install)

Can you absolutely confirm that the name of the taxonomy is the correct one?

I made a mistake, I was using the taxonmy slug of each category and not the golobal slug category, now it is working. Thank you.