Why can Apple xs max send MMS but not SMS?

The processing method that the mobile phone cannot send short messages is as follows:

First, you can change your mobile phone and see if you can send and receive text messages;

Second, if you can send and receive short messages, I suggest you plug the card back into your mobile phone and send yourself a short message to see if you can receive it.

Third, if not, I suggest you check whether there is a problem with the sim card.

4. Check whether the number of the SMS center is set correctly;

5. Bring the mobile phone card to the local business hall for testing or replacement.