I have a problem sending messages
I have issues sentinel
and arriving messages
iPhone 11 Pro Max, iOS 15
Question marked as
Try first to optimize the range of the mobile network, see this Apple article:
If you see No Service or Searching on your iPhone or iPad
If you see No Service or Searching on your iPhone or iPad - Apple Support
Then see -> If you can't send or receive messages on your iPhone, iPad, or iPod touch
If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support