iphone is showing 1 unread message when there are none

Just solved this for myself: settings>messages>message filtering. Turn on Filter Unknown Senders. Open iMessage. You should now be able to see a Filters button at top left (on iPhone). Tap that. Now you should see a list of folders which should show you where your unread message is. (Mine was in Unknown Senders folders).

Hope this helps.

Try a forced restart.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

Force restart iPhone - Apple Support (IN) Force restart iPhone - Apple Support (IN)

this did not work.