12306 why was there no notice after the ticket purchase was successful?

If the reservation is successful, then the purchase is successful. There are two reasons for not receiving the text message. One is that the bound mobile phone number may be wrong, or it is bound to someone else's mobile phone. The second is that your mobile phone is set to refuse to accept some commercial SMS notifications, so you didn't receive them. You can go to the mobile phone interception place to see if there is any intercepted notice, and you can receive it by contacting interception in the mobile phone settings.