If you are getting the following error message on your Youzify Actitivty page:
"Notice: Undefined index: in /nas/content/staging/aardvarkdemo/wp-content/plugins/youzify/includes/public/core/wall/yz-class-privacy.php on line 255"
Add the following code to your functions.php file and then refresh the Activity page twice. Now remove the code from your functions.php file and this should fix the issue.