For the past couple of months, I've been having a 1 on the Message app icon, that I cannot seem to get rid of. 

I've checked everywhere, I've got no new unread message. I restarted phone, marked all messages "as read" in the app, but nothing seems to clear this 1 new unread message

I tried all I can think of, including all from the below site...

https://www.technobezz.com/

fix-android-device-showing-unread-sms-messages/

Can anyone help provide a solution that actually works?

Thanks in advance