On the desktop version of Facebook, there seems to be an annoying bug in the page notifications feature. You see, when somebody interacts with one of your page’s posts, that interaction shows up as an unread notification under the Activity tab.
An example of what the Activity tab looks like when your page has an unread notification:
As you soon as you click on the Activity tab, those notifications are supposed to be marked as “read”. i.e. The red icon beside the word “Activity” should disappear.
Unfortunately, there seems to be an intermittent bug that prevents notifications from being marked as read. This occurs every now and again, leading to a frustrating issue where the Activity tab is always showing the “unread” notification icon. I’m not sure what causes it; all I know is that it happens enough to be an issue.
There is a simple fix for this issue. On the right side of the page, you should see a small column that contains the following:
If you click on the “Notification” link, it seems to mark all unread notifications as read.
Another fix is to read said notifications on your smartphone, as the bug doesn’t seem to exist on the mobile version of Facebook.