Having trouble
When I send a iMessage it disappeared and it didn’t send
iPhone 11 Pro Max, iOS 18
Question marked as
If you're using a beta version of iOS, as your profile indicates, then it may well just be a bug. You can try Apple's suggestions here:
If you can't send or receive messages on your iPhone or iPad - Apple Support
but it may well be something that you'll need to wait for the release version of iOS, or revert back to the current version, to fix.
Regards.