Why can't a few mobile phones receive short messages in the process of sending short messages in groups?

Note: Mobile phone users who can't normally receive group SMS messages include: users who owe money to stop, the signal is abnormal, the information stored in the mobile phone is full, the mobile phone is unsubscribed, incoming calls are prohibited, and users who have complained to the operator. 1. The mobile phone is turned off or stopped for more than 24 hours or 48 hours (the time range varies from operator to operator); 2. The inbox in the mobile phone is full; 3. There may be a problem with the information center setting of the mobile phone; 4. The system mode settings of individual mobile phones do not match, which may also lead to poor information reception. 5. Short messages must be transmitted through the Internet and wireless network, which will inevitably lead to certain errors and very little data loss. 6. From the user's reception, the numbers sent by customers may include high-end numbers and cancellation numbers, and it is impossible to receive every number.