Are you a group administrator and have configured your group so that all new members need to be approved to be part of it? Then you will need to approve users that request to become new users:
1. You will receive an e-mail to your registered e-maikl address with a link to accept of decline the request.
2. Alternatively, you can enter the group in KAddENA -> Click the "Options" drop down menu -> Click "Manage Members" -> Select "pending" and "approve" in the drop-down.