In particular circumstances, if an administrator for a site also adds themselves to a Research Directory the short name editing field can be removed from their set up.

To turn this back on:

• Go to 'Site Setup' and select 'Users and Groups'
• Click the 'show all' link and find your entry in the list of users
• Select the link for your user name in the left column, which will take you to your User Properties.
• Look down the page until you find 'Allow editing of Short Names', which will have become unchecked, and check it then save the change.
• Your default setting should now be restored.