Apple 13 Zhihu WeChat is authorized not to send SMS.

The message could not be sent due to the following reasons:

1. The mobile phone network is unstable. We can check the mobile phone network by opening the webpage.

2. SMS can't be sent out, maybe there is something wrong with the SMS center. Check the signal.

3. A firewall is set up, which makes it impossible to receive information.

You can try to restart or replace the phone for testing and checking.

1. Whether the SMS center number is set incorrectly, please re-enter the correct SMS center number;

2. No signal or low battery;

3. Because the system is busy during the holiday short message sending peak period, it is suggested that you try again later or avoid the sending peak period;

4. The sending format is incorrect. If you send a short message to PHS users, you need to add the area code before the number;