Register Activation hook won't call method

This code is located in my plugin class file. I can get the echo statement in the constructor to show up just fine, but for some reason it just won't call the method. Any ideas?

public function __construct($plugin_name, $version)
{
    $this->plugin_name = $plugin_name;
    $this->version = $version;
    echo "here";
    register_activation_hook(__FILE__, array($this, 'create_plugin_database_table' ));
}

public function create_plugin_database_table()
{
    echo "here";

    global $wpdb;
    $table_name = $wpdb->prefix . 'sandbox';
    $sql = "CREATE TABLE $table_name (
       id mediumint(9) unsigned NOT NULL AUTO_INCREMENT
       );";

    require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
    dbDelta($sql);
}

via Chebli Mohamed