Shefki, thank you for clarification.
Any user account must be a member of the 'user' role as well, even if a new role has been created, right? (a member of a new role and the 'user' role).
Is "UI Configuration" the only part of the configuration tree that needs to be configured for the new role (permissions, AET drop-down list....)?
It looks like, when a new "AET drop-down list" is created, it should (must?) be created for both Internal and External. I have created an Internal list and skipped an External one, I was unable to open an internal AET. When an external was created everything worked fine, besides that problem mentioned in my initial post.