iPhone "message failed to send" error
When I restart my iPhone I get a "message failed to send" error" on the screen. I cannot find the message in Messages nor can I find a means to clear the repeating error message.
iPhone 6, iOS 12
This could be a message stuck on the iMessage server somewhere. I would try to log out of your iMessage or turn it off in your Settings->Messages then reboot the phone and see if it persists.