Okay, I’ve solved my issue (so soon!?!?).
I’ll leave this post here in case someone else has this issue.
The WordPress Codex says:
Add the $max_pages parameter to the next_posts_link() function when querying the loop with WP_Query
I did initially do this by replacing:
<?php next_posts_link( 'More' ); ?>
with
<?php echo get_next_posts_link( 'Older Entries', $the_query->max_num_pages );
from an online tutorial but I forgot to change ‘$the_query‘ to ‘$query‘.
So to confirm, if you are using WP_Query to query your loop, you need to use <?php echo get_next_posts_link( 'Older Entries', $the_query->max_num_pages ); for pagination.
