Why can't I get the verification code when booking train tickets online?

You can't receive SMS or verification code due to the following reasons:

First, you can check whether the mailbox is full first. If it is full, please delete some information.

Second, you still can't get it after deleting it. You can change the machine or card to see if it is a hardware factor;

Third, after eliminating the above reasons, we can try to see if it can be received in other places to see if it is the reason for the weak local signal.