The SMS prompt is not turned on.

The inbox is full, and some security software (such as 360) will intercept or filter the messages.

1. Inbox is full: some short messages cannot be received normally. You can check the message option in the phone settings to confirm whether you can't receive unread messages because your inbox is full. If this is the case, you can try to delete some unnecessary messages to make room for receiving new messages.

2. Some security software (such as 360) intercepted or filtered these short messages, resulting in these short messages not being received normally. You can check your phone's security software settings to see if you can't receive unread messages because of interception or filtering. If this is the case, you can try to turn off or modify the blocking or filtering settings of security software so that you can receive these short messages normally.