Board Thread:Support Requests - Getting Technical/@comment-5116706-20130513024015/@comment-957747-20130513034730

It was because Johnny Thunder deleted a lot of pages (see the deletion logs). The Wiki Activity module scans the last X amount of Recent Changes to a wiki and displays only certain edits. If the last ~300 changes on a wiki was file deletions, the wiki activity module would show nothing since deletions are not displayed in Special:WikiActivity.

Also, since there has been recent activity after the deletions, WikiActivity is now showing results.