Thanks for your very useful plugin!
It seems to me that there is a bug in UAM dealing with custom WordPress user roles (e.g. defined via User Role Editor). If a custom user role's ID has more than 11 characters (e.g. "contentmanagers") then UAM can't handle these user roles, because the database field "object_id" within the table "wp_uam_accessgroup_to_object", where the user role ID's are stored, is limited to 11 characters. So if you assign the above mentioned user role "contentmanagers" to your user group in UAM the value that is stored would be "contentmana". UAM will then not be able to give theses user roles the necessary access.
After increasing the number of characters of "object_id" everything worked fine.