Unable to unhide a link in the Application Navigator
In Confluence 5.4.x, if you hide one of the links in the application navigator (Confluence Admin > Application Navigator), it is not possible to unhide it as the part of the row where the Update button should be is blank.
This is caused by an undocumented bug.
This problem is resolved in Confluence 5.5. Upgrade to that version or later to be able to unhide links in the application navigator.