This explicit code is missing from your example and you should verify that you have at least these statements (plus any additional post tag functions, or analogous calls to “the_content()”) included exactly as this in your original code:
while ( $the_query->have_posts() ) : $the_query->the_post();
the_content();
endwhile;
This should roughly be at the location noted by this comment in your code:
// The Loop
If your while statement is not specifically calling methods of $the_query, that would call up a default query that has already been run and that does not match your category query.