O365 groups disappear on Outlook

Hi all,

I've an issue with my O365 groups. 

When I right click on my Groups, I can browse all the groups and select one of the to add myself on it.

Unfortunately, few seconds after adding this group to my list, it disappears and I cannot see it in my list.

I see I'm a member of the O365 group my I'm not able to add it in my list.

When I go the the Outlook online, in some groups I see "follow in the inbox" and not for the other ones.

Please someone can give me a solution? Is it possible to recreate the group?