dtm_can_download custom filter

Hello,

I have this business requirement :

Only allow members to download files if they downloaded less than 20 differents download this month.

So I tried this code in fonctions.php :

add_filter( 'dlm_can_download', array( $this, 'check_custom_rule' ), 10, 2 );
function check_custom_rule( $can_download, $download){
	if ( false !== $can_download && $download->is_members_only() ) {
		if (is_user_logged_in() ) {
			$current_user = wp_get_current_user();
			$current_user->ID;
			$querystr = "SELECT count(DISTINCT download_id) as count FROM wp_download_log WHERE user_id=$current_user->ID AND YEAR(download_date) = YEAR(NOW()) AND MONTH(download_date) = MONTH(NOW())";
			$result = $wpdb->get_results($querystr, OBJECT);
			$nb_of_dl_this_month =  $result[0]->count;
			if($nb_of_dl_this_month > 20 ){
				$can_download = false;
			} else {
				$can_download = true;
			}
		}
	}
	return $can_download;
}

But I got access access denied all the time even if I have downloaded only 1 file.
When I excecute this code outside of the filter, I got $can_download to true.
So smth wrong with the way I implemented this filter ?

Thanks a lot ??

Regards,

Dorian