Hi Errico,
I've tried to look at your browser ajax call for those notifications, actually it was called perfectly fine
http://screencast.com/t/DmhhXUyN5O
The reason why it will not updated the notification as there have new notification (for example new message instantly) is because it got delay on the notification interval that have been set hard-codedly (which is the notification will be checked every 50 second by ajax call)
Refer these screenshots:
http://screencast.com/t/RZmOBxpy2qp http://screencast.com/t/IGliaF1P0
However, if you prefer the notification to be checked more frequent, you can do template override for this file:
JoomlaFolder/components/com_easysocial/themes/wireframe/structure/default.js
and change the code on Line 42
"interval": <?php echo SOCIAL_NOTIFICATION_POLLING_INTERVAL; ?>,
To
"interval": 6,
Where you can set how many second system to check the notification (number 6 above you can configure as you prefer), I suggest not set it to low because it might caused your site to work more(heavy).
You're suggested to backup the file that you want to edit/template override beforehand for precaution