Pagination not working - FrontPage

So in the comments you said:

if I click on the 2nd or 3rd or whatever page number, it's redirecting me to the same page (front page)

And that's because your query args ($query) is missing the paged argument which is needed for paginating the posts.

So make sure to add that arg to your query. E.g. using array:

$query = array(
    'posts_per_page' => 6,
    'paged'          => get_query_var( 'page' ),
);

Note that I assumed you are actually using a static front page, hence I used get_query_var( 'page' ) and not get_query_var( 'paged' ) (note the page vs paged — in the $query though, it is paged).

So you should also use that with paginate_links():

echo paginate_links( array(
    ... your args.
    'current'      => max( 1, get_query_var( 'page' ) ), // use 'page' and not 'paged'
    ... your args.
) );

BTW, in the question, (it seemed like) you made a typo: That $query->max_num_pages should be $queryObject->max_num_pages.

And if you're not actually using a static front page, then you should, to avoid 404 errors with the pagination due to a conflict with the main WordPress query.

Update

(Sorry, I didn't really notice the add_shortcode() call in your code.)

No Output! What I'm missing?

As pointed in the comments, shortcodes must return the final output and not echoed, and that a shortcode function should not echo anything else. Otherwise, the output would be misplaced in the post content, and causes a JSON error in the REST API response and results in a failure in saving the post via the Gutenberg/block editor. And those are just two sample issues that could happen.

So if your shortcode uses a complex HTML markup, you could use output buffering; otherwise, just store the output in a variable and then return it. Simplified example:

// Using output buffering:
function simpleblog() {
    ob_start();
    ?>
        some complex HTML
    <?php
    return ob_get_clean();
}

// Storing to a variable:
function simpleblog() {
    $output = '';

    // ... your code here; no 'echo' calls.
    $output .= 'foo bar';

    return $output;
}

Further Reading

• https://codex.wordpress.org/Pagination
• https://codex.wordpress.org/Shortcode_API

I use this on archive pages. If you are trying to use it elsewhere then that might be a cause of the issue.

if ( ! function_exists( '_s_pagination_links' ) ) :
/**
 * Numbered pagination
 */
function _s_pagination_links() {
    global $wp_query;

    $total_pages = $wp_query->max_num_pages;

    if ($total_pages > 1){
        $current_page = max(1, get_query_var('paged'));

        echo paginate_links(array(
            'base' => get_pagenum_link(1) . '%_%',
            'format' => 'page/%#%',
            'type'      => 'list',
            'current' => $current_page,
            'total' => $total_pages,
        ));
    }
}
endif;