What does the red exclamation mark on the text message mean?

There is a red exclamation mark on Apple's mobile phone message, because the short message can't be sent. You need to restart the "iMessage" function. The specific operation method is as follows:

1. First open the Apple 8 phone and click the "Settings" system icon.

2. Then click the "Information" option, as shown in the figure below.

3. Then turn on the "iMessage" option on the right, shut down and restart.

4. If you want to clear the exclamation mark on the message, you need to restart the Apple phone.

5. When waiting to turn on the Apple phone again, click the "Info" icon again.

6. Then send the unsent message.