Unable to upade Appointments+ Plugin

Hi

I have clicked on the "WPMU DEV updates are available: Please review your available updates today"! in dashboard of my WP and nothing happens ...
Plus I have a Warning message on the Plugin Page

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'Wpmudev-updates::index' was given in /home/surreylo/public_html/wp-includes/plugin.php on line 406

Thanks