Group notifications problem

I have a problem with group notifications. Neither site nor email notifcations are received by me or group members when new content is added to the group I am/they are a member of.
My setup is quite minimal:
Latest egg version (1.92)
I have  created just one  group. I am only using the default plugins that come with the default elgg installation. I am NOT using any third party plug-ins.
My group notifications settings are set to receive notifications both by email and on site, see the screenshot below:
http://imgur.com/no4UHEw
I know my email settings are configured correctly because emails are sent by elgg for new user registrations. 
Emails are also sent when someone clicks on the "like" icon to inform users that someone likes their content.

I know that similar questions have benn posted before https://community.elgg.org/discussion/view/1160359/not-getting-any-email-notifications?offset=10
but I really can't  find a solution to what seems rather a simple problem and all this is quite frustrating.
Any help would be greatly appreciated.