Problem with query loop pagination

I have a custom query loop (I don’t use the posts module because it doesn’t suit me for design reasons). And I need to add pagination to it, because there are about 600 different entries in the directory… But it doesn’t work.
In the Pagination settings, I first chose the query I want it to apply to and at the end, I enabled Ajax…
But it doesn’t work. What am I doing wrong?

Thank you so much