WP Pagination on page filtered by category not working

My Wordpress index page includes the WP Pagination bric.

The page filters posts by a specific category ID.

When I generate the theme, there are more pages than posts. I presume the pagination is counting all the pages but the filter is excluding them.

How do I use the pagination widget on a page filtered by categories?

Any chance you could share a live URL or some more info on this so I can try and help.