As reported in Annotum Issue #36, in some cases clicking on an author's name results in a blank page.

For example, URLs like:

http://demo.annotum.org/author/annotum2go/

or

http://demo.annotum.org/?author=1

should display a brief author profile, followed by a listing of all posts and articles by that author.  If instead you see a blank page, or only the heading "Recent Posts" with no other content, then you need to set up permalinks.  

To do this, 

1. Go to Dashboard > Settings > Permalinks
   
2. Select any setting for permalinks other than the default, e.g. Month and Name as shown below.
   
3. Click "save changes"