Wordpress WP_Query with pagination

I have been googling and having a look many other questions related to this one but the problem still persist.

I'm trying to get a paginated query and only page 1 is shown. If you change the paged variable to any other number, it returns an empty array.

Here is the code I used, that is very similar than others I've seen in other questions:

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$temp = $wp_query;
$wp_query= null;
$args = array(
              'posts_per_page' => 20,
              'post_type'      => 'post',
              'paged'          => $paged,
              'category_name'  => 'blog'
);
$wp_query = new WP_Query($args);
$data = array();
while ($wp_query->have_posts()) : $wp_query->the_post();
    $obj = new stdClass;
    $obj->id              = $post->ID;
    $obj->title           = $post->post_title;
    $obj->excerpt         = substr(str_replace(array("\r","\t","\n"), array('','',''), trim(strip_tags($post->post_content))), 0, 200).'...';
    $obj->slug            = str_replace('http://localhost/', '', get_permalink($post->ID));
    $obj->author_name     = get_user_by('id', $post->post_author)->user_login;
    $obj->featured_image  = wp_get_attachment_url( get_post_thumbnail_id($post->ID, 'post-thumbnails') );
    array_push($data, $obj);
endwhile;

What's wrong? I can not guess it!

Write this in your functions.php

//Pagination
function custom_pagination($numpages = '', $pagerange = '', $paged='') {

if (empty($pagerange)) {
    $pagerange = 2;
}

/**
 * This first part of our function is a fallback
 * for custom pagination inside a regular loop that
 * uses the global $paged and global $wp_query variables.
 *
 * It's good because we can now override default pagination
 * in our theme, and use this function in default queries
 * and custom queries.
 */
global $paged;
if (empty($paged)) {
    $paged = 1;
}
if ($numpages == '') {
    global $wp_query;
    $numpages = $wp_query->max_num_pages;
    if(!$numpages) {
        $numpages = 1;
    }
}

/**
 * We construct the pagination arguments to enter into our paginate_links
 * function.
 */
$pagination_args = array(
    'base'            => get_pagenum_link(1) . '%_%',
    'format'          => 'page/%#%',
    'total'           => $numpages,
    'current'         => $paged,
    'show_all'        => False,
    'end_size'        => 1,
    'mid_size'        => $pagerange,
    'prev_next'       => True,
    'prev_text'       => __('«'),
    'next_text'       => __('»'),
    'type'            => 'plain',
    'add_args'        => false,
    'add_fragment'    => ''
);

$paginate_links = paginate_links($pagination_args);

if ($paginate_links) {
    echo "<nav class='custom-pagination'>";
    echo "<span class='page-numbers page-num'>Page " . $paged . " of " . $numpages . "</span> ";
    echo $paginate_links;
    echo "</nav>";
}
}

And use the following code wherever u want to display pagination

<?php
        if (function_exists(custom_pagination)) {
            custom_pagination($cat->max_num_pages,"",$paged);
        }
        ?>