[4.1 Alpha 1] XF Current visitors: Viewing unknown page
It appears that VaultWiki 4.1 doesn't currently tell XenForo what to display in Current visitors for VW pages, and as such XenForo says that someone looking at the wiki is "Viewing unknown page"
XenForo 2.x is looking for a static function in the controller, getActivityDetails(array $activities) {}.