Tags autocomplete not showing results

When creating or modifying a page, the "Tags" field in the "Document Information" section does not auto-complete. When a known value is typed into the box, the message "No Results!" is displayed.

Steps to cause problem
1. Visit the wiki using path based access
http://localhost:8080/xwiki/wiki/testwiki/
2. Create a new page
http://localhost:8080/xwiki/wiki/testwiki/edit/Main/testpage?template=&parent=&title=testpage
3. Type a known value into the Tags field

The message "No Results!" is displayed instead of the known tag.