Situation:

AFS denies access inspite of Network Identity Manager (NIM)-Login.
The symbol of the NIM is an empty white cube and in front of the lock is a red cross. Only 'Kerberos v5 credentials' appears in the NIM but not 'AFS tokens'.

Solution:

• NIM: Login with identifier (name) and password in the upper left corner click onto the symbol with the yellow star)
• Now from the menu 'Options' choose the tab 'General'
• In the tree on the left under “Identities” select your own identifier
• Now click on tab 'AFS' and in the textarea behind 'Cell' enter: math.uni-hamburg.de
• Click on the 'Add / Update' button
• In the big textarea below appears the text 'math.uni-hamburg.de' (Auto)
• Click on the text then onto the 'Apply' and 'OK' button
• Renew yor credentials by clicking onto the symbol with the green star

Now, beside the 'Kereberos v5 credentials' also 'AFS tokens' appear in the NIM (Network Identity Manager). In addition the red cross in front of the lock is vanished and the access granted.