Here's how to troubleshoot your iPhone
when your messages aren't going through.
First, tap "Try Again."
If that doesn't work,
try these three fixes.
Check your network connection.
If you don't have good cell service or strong WiFi,
you won't be able to send messages,
even if your phone is working fine.
Make sure you're not in airplane mode.
Swipe up from the bottom
or down from the top of your iPhone
and make sure the airplane icon
on the upper-left corner is not enabled.
Then check your iPhone's messages settings.
In the settings app, find and click "Messages."
Then make sure the switches next to "iMessage"
and "Send as SMS"
are toggled on, to green.
You should also make sure
you're texting the right number.
Restart your phone by holding down the power button
and try sending your message again.
Lastly, try resetting your network settings.
Navigate through the settings app to the "General" tab,
then click "Reset,"
followed by "Reset Network Settings."