What is the reason why it took a long time to receive the SMS receipt after sending the SMS?

After sending a message, the message receipt is not received or received after a long time, which may be caused by the following situations: 1) The message receipt is lost in the network transmission process, but this probability is very small. 2) System maintenance, which cannot be handled temporarily, can be resumed after the system is normal. 3) There is a delay in the network, and a receipt will be received later. 4) Personalize and block some types of receipts. 5) I chose lightning short message and changed my mobile phone, but the new mobile phone does not support lightning short message. For more service offers, click on "official website" Customer Service 4 below to answer your questions.