Why does my IPHONE ring after sending text messages, but it doesn't ring when receiving text messages? Please help me ~ ~ ~

I don't know what version you are using,

Anyway, I use the second generation 3.0 firmware:

Turn on the settings-sound ring bar to see if the sound is turned off, because that sound is usually not noticed. If the bar is at the far left, it means that the ringtone has been turned off. Turn it back.

If there is still no sound, turn on 9 1 and check whether the system audio in your body has been accidentally replaced.