The fixing step was the missing one.
Magically the new forums appeared in kunena, associated to the corresponding GJ Groups, after the fix. I understand now why the assignment of permissions is not necessary.
But with the solution appeared a new problem. We need to group many subforums inside a category (a GJ restricted category). And need that the permission of the parent group (related to a GJ group) is inherited to their subforums.
I have this
Group A (associated to a GJ Group A) and Gourp B (associated to a GJ Group
And inside Group A we have Subforum A1 and Subforum A2.
I need that only the users of GJ group A could access Subforum A1 and Subforum A2. Users of Group B shouldn't access Group A, neither its subforums A1 and A2. Is that possible? I made some tests, but could not get it. I tried different permissions types on the subforums (CB and Access Level)
Regards