In order to get the notification while a user is online, busy or Offline then follow the following steps to configure this.
Kindly login to CometChat Admin Panel.
From left menu "Settings->general"
Search for "If yes, user offline notification will be displayed:", "If yes, user busy notification will be displayed:", "If yes, user online notification will be displayed:" and do the respective changes.
As shown below in the screenshot
"Clear Cache" from the left menu
Clear browser cache.
Now check, if your changes get reflected on site or not.