pre_get_posts pagination not working

Instead of having $q->set( 'posts_per_page', 12 ) in the pre-get-posts function, I use the Read Settings ‘Blog pages show at most’ and that seemed to clear things up.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)