Hi all,
I had the same problem so I took a look around. In lines 28 to 31 of “plugins/wp-user-avatar/includes/class-wp-user-avatar” I notice that the author has commented out lines 29 and 31 which look to be responsible for putting the avatar edit box onto the page.
// Profile functions and scripts
//add_action('show_user_profile', array('wp_user_avatar', 'wpua_action_show_user_profile'));
add_action('personal_options_update', array($this, 'wpua_action_process_option_update'));
//add_action('edit_user_profile', array('wp_user_avatar', 'wpua_action_show_user_profile'));
I’m not sure the reasoning for this, but you can uncomment these lines and it appears again. I took a safe option and reverted back to version 2.2.7 of this plugin until there is an official fix.
Hope this helps.