I sent a WeChat message to the other party, and the mobile phone showed "Message sending failed, and the other party didn't add you as a friend". What is the reason?

There are two situations. One is that your mobile phone is not connected to the internet, so the message cannot be sent out. The other is that the other party didn't add you as a friend or he has blacked you out or deleted you, so there are two situations. One is that your mobile phone is not connected to the internet, and the other is that the other party has not added you as a friend or he has blacked you out or deleted you, so there will be such a prompt.