Idiom column doesn’t appear in “Edit Pages”

I’ve used polylang for three other sites I’ve created, this is the first time I’ve had this problem: in “edit pages” one of the idiom columns (with the flag, signaling in which language the post is written) simply doesn’t appear. It’s in fact the main idiom!
Another thing is that the pages written in that language remain, but are signaled as another language. When I change the idiom of wp, the missing flag reappers, but now the other two disappear.
I don’t if I explained myself properly, english is not my first language, please ask if something is unclear.