Old Apple can't send text messages.

Take Apple's system as an example. The reasons why Apple's mobile phone can't send short messages and the solutions are as follows: 1. Check whether the mobile phone is in arrears. When the mobile phone is in arrears, functions such as sending and receiving text messages and making phone calls cannot be used, so the phone bill should be recharged in time. 2. Check whether the cell phone signal is good. If the cell phone signal is blocked or the signal is not good, it will affect the sending of short messages. Move to a place with a good signal and try to send it again. 3. Maybe the SIM card is loose or damaged. Plug and unplug the SIM card again, or replace it with a new SIM card to see if it can be used normally. 4. It may also be caused by system failure. Click "Settings", click "General", find the "Restore" option in the drop-down list, click "Restore Network Settings", and then restart the phone to see if it can be solved. 5. Important data can also be backed up and restored to factory settings, or sent to after-sales maintenance. This answer applies to most of Apple's mobile phone models.