Apple phones can't send text messages. What happened?

# Apple's mobile phone can't send short messages, which may be caused by system failure. Apple mobile phone can't send text messages. What's going on here? We need to operate (3 steps). The model of this demonstration is iPhone13; . System: IOs15.1; +0; The following are the detailed steps:

1 Click General.

In the phone settings, turn on the general options;

1. Click Universal 2, and then click Restore iPhone.

After entering, turn on the transmission or restore the iPhone；;

2. Click Restore iPhone3, and then click Restore.

After entering, click Restore.

3. Click Restore