iMac and iPad Show Unread Message

Both my new iMac (Sequoia 15.6.1) and my iPad (18.6.1) always show the red dot above the Messags app indicating an unread message. It does no show on my iPhone. I asked Siri on the iMac to read unread messages, but she says there are none. I have shut down all the units multiple times over two weeks to try to eliminate this issue. When I restart, the numbers go away, but only until I start receiving messages again. Is there any way other than restarts to get rid of this annoyance?