Create Event button doesn't appear in a group for non-superusers

Hello,
As far as I can see, I have the permissions set correctly and group members should be able to create new events within that group. However the button only appears if I'm logged in with my super user account. If I test it with an account that belongs to one of the ES profile types, I don't see that button, even if I'm the admin of that group.
Thanks for looking into it,
Michael