There are two issues that some community members have been running into with the community Inbox functionality. Both issues are easy to fix and will be explained below.
Inbox shows incorrect "Unread" count
Issue: In this situation, the two inbox counts on the screen (top-right and left) show that there is one unread item, even though the inbox does not have any unread notifications.
Solution: Click the "Mark all read" button on the inbox to clear the "1" flag.
Inbox items revert to unread after reading
Issue: When reading your inbox, the notifications are being marked as "read" as expected. However, when you refresh your inbox or go to another page, your inbox count goes back to what it was previously and items are marked as "unread" again.
Solution: This was caused by an error in the community site's cache which has since been fixed. However, an additional step is needed for affected users. To clear this, please use the community's "Log Out" button to force the logout process and then log back in as normal. Logging out through the standard inactivity timeout will NOT fix this issue.