Texting always reminds me of the reason why it was not delivered. That man's cell phone is on or off!

First, you need to check whether the SMS access code in your mobile phone is correct. You can call the operator at 10086 Unicom 100 10. If the settings are correct, see if others can receive the message. If someone else can receive it, it means that there is something wrong with that person's mobile phone, such as his blacklist or SMS center code.