Unread message in Messages not being set as "read"

Solution 1:

This problem is fixed in a new release of 10.10.2

I'm currently running 10.10.3 and am having this issue again, so not fixed in 10.10.2 unfortunately. Have experienced in the past, major pain.

The following works for me every time

In the Finder > Go Menu > Go to Folder type (Copy and Paste) ~/Library/Preferences into the Dialogue box.In the Preferences find the com.apple.imessages.bag.plist and drag it to the Trash.

(found on https://discussions.apple.com/thread/4486753?start=0&tstart=0)

Then reboot the machine. The post says to reboot messages but I always have to reboot the entire computer for this to work properly.

Solution 2:

I had this problem too. I disconnected all accounts in messenger, disabled handover, rebooted, and added accounts again + enabled handover. This solved the problem.

This problem is fixed in a new release of 10.10.2

Solution 3:

I right clicked on the icon and it showed what message was unread. I clicked on Digital Post (1 unread) and it took me to the message but the red dot was still there. So I replied to the message and the red dot disappeared. Not sure if that works for everyone but it worked for me this time!