Homepage excluded category not showing in single post

On my site, I have a booking blotter I made to connect with the local Sheriff’s office:

https://ellatinodigital.com/categoria/detenidos/

I filter them out from the home page with a filter function in functions.php.

The problem I’m having is this:

If you click on an individual to go to a single post view, it says that the post does not exist. This is not correct.

The post is in the database and neither the slug nor the direct “?p=#” work.

I believe that somehow, it is being blocked beyond just the homepage.

My filter function is below:

function exclude_category_home( $query ) {
    if ( $query->is_home ) {
        $query->set( 'cat', '-400' );
    }
return $query;
}

add_filter( 'pre_get_posts', 'exclude_category_home' );

I’m a very good developer but I am new to the WordPress platform.

I appreciate your time and consideration.