Apple sent six text messages saying it was not delivered.

1. If the mobile phone can't send short messages, troubleshooting can be carried out according to the following conditions:

(1) SMS center number is set incorrectly, please re-enter the correct SMS center number;

(2) No signal or insufficient battery power;

(3) The mobile phone shields the short message sending function;

(4) blacklisted by SMS;

(5) Insufficient quantity balance.

2. If you still can't solve the problem after self-troubleshooting, it is recommended that you contact local manual customer service to assist in verification and handling.