Problem

Workbox notification icon  (introduced in Confluence version 4.3) is not displaying when using Chrome and having the Do Not Track Plus Chrome extension enabled.

Cause

The corresponding extension is made to avoid websites track you. Apparently it recognizes the workbox notification icon as a potential risk.

Workaround

Disabling the extension solves the issue, however adding the Confluence site to its whitelist might be a considerable option, but in some cases this does not fix the issue.