Force refresh your browser (ctrl+f5) and the announcement comes back again as being unread. Also, if you actually go to https://app.plex.tv/desktop/#!/announcements you will see the unread icon on the right corner even after its been read multiple times.
This continually happens when plex push out something to the announcement page. See the threads below as two more examples …
If the past is anything to go by they’ll get it sorted in a few days.
