[Plugin: WP-PageNavi] Pagination doesnt work with post types plugin

Hi i try to use Wp Page Navi on a custom post types but it doesnt work. It shows but the navigation doesnt work. Here is my code :

<?php $custom_query = new WP_Query();
				$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
				$custom_query = new WP_Query('cat=6&paged=' . $paged.'&posts_per_page=2');
				while($custom_query->have_posts()) : $custom_query->the_post(); ?>
					<li>

					<?php
						$img="";
						$args = array(
						'post_parent'    => $post->ID,
						'post_type'      => 'attachment',
						'numberposts'    => 1,
						'post_mime_type' => 'image'
						);
						$attachs = get_posts($args);
						$img=wp_get_attachment_image_src($attachs[0]->ID,'full');
					?>

					<div id="colonne-prod-df-img"><img src="<?php thumbGen($img[0],136,172,additional_parameters); ?>"></div>
					<h1><?php cuttextmaxtit($post->post_title,30); ?></h1>
					<p class="detail-prods"></p>
					<p class="detail-prods-sub"><?php echo excerpt(80); ?></p>
					<p><a href="<?php the_permalink(); ?>">Voir le produit ></a></p>
					</li>
			<?php endwhile; ?>

			</ul>

			<div id="pages-next"><?php if(function_exists('wp_pagenavi')) { wp_pagenavi(); } ?></div>

https://www.ads-software.com/extend/plugins/wp-pagenavi/