Pagination custom query

I am trying to make a custom page template that shows the most viewed posts. I can return posts but I am having trouble figuring out how to paginate it. Here is what I have:

$args = array('orderby' => 'meta_value_num', 'meta_key' => 'post_views_count', 'posts_per_page' => 36 );
            $loop = new WP_Query( $args );
            while ( $loop->have_posts() ) : $loop->the_post();

I tried:

$paged = ( get_query_var('paged') ) ? get_query_var('paged') : 1; 
            $args = array('paged' => $paged, 'orderby' => 'meta_value_num', 'meta_key' => 'post_views_count', 'posts_per_page' => 36 );
            $loop = new WP_Query( $args );
            while ( $loop->have_posts() ) : $loop->the_post();

but my pagination still doesn’t show up. I am wondering if it has to do with my pagination function or the way I am setting up my query.

I just call my pagination function below the query, it all looks like this:

<?php
            $paged = ( get_query_var('paged') ) ? get_query_var('paged') : 1; 
            $args = array('paged' => $paged, 'orderby' => 'meta_value_num', 'meta_key' => 'post_views_count', 'posts_per_page' => 36 );
            $loop = new WP_Query( $args );
            while ( $loop->have_posts() ) : $loop->the_post();?>
                <?php get_template_part( 'content', get_post_format() ); ?>
            <?php endwhile; ?>
        <?php wp_reset_postdata(); ?>

<?php pagination(); ?>

This is my pagination function:

if ( ! function_exists( 'pagination' ) ) :
    function pagination() {
        global $wp_query;

        $big = 999999999; // need an unlikely integer

        echo paginate_links( array(
            'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
            'format' => '?paged=%#%',
            'current' => max( 1, get_query_var('paged') ),
            'total' => $wp_query->max_num_pages,
            'mid_size' => 1,
            'prev_text'    => __('«'),
            'next_text'    => __('»'),
            'type'         => 'list'
        ) );
    }
endif;

Any help would be greatly appreciated.

This is a local/global variable problem. It can be solved either by changing the pagination function to work with local variable, or by promoting the local variable into global scope. As you are using wp_reset_postdata(), i guess you want to keep the original query.

Change the pagination function to accept arguments –

if ( ! function_exists( 'pagination' ) ) :

    function pagination( $paged = '', $max_page="" ) {
        $big = 999999999; // need an unlikely integer
        if( ! $paged ) {
            $paged = get_query_var('paged');
        }

        if( ! $max_page ) {
            global $wp_query;
            $max_page = isset( $wp_query->max_num_pages ) ? $wp_query->max_num_pages : 1;
        }

        echo paginate_links( array(
            'base'       => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
            'format'     => '?paged=%#%',
            'current'    => max( 1, $paged ),
            'total'      => $max_page,
            'mid_size'   => 1,
            'prev_text'  => __( '«' ),
            'next_text'  => __( '»' ),
            'type'       => 'list'
        ) );
    }
endif;

And the loop template will be like –

$paged = ( get_query_var( 'paged' ) ) ? get_query_var( 'paged' ) : 1; 
$args = array(
    'paged'          => $paged, 
    'orderby'        => 'meta_value_num', 
    'meta_key'       => 'post_views_count', 
    'posts_per_page' => 36 
);
$loop = new WP_Query( $args );

if ( $loop->have_posts() ) :
    while ( $loop->have_posts() ) : 
        $loop->the_post();
        get_template_part( 'content', get_post_format() );
    endwhile;

    pagination( $paged, $loop->max_num_pages); // Pagination Function
endif;

wp_reset_postdata();