My cousin has been missing for four days. The phone is on, but the WeChat message is not answered or returned. What should I do?

Send an urgent message first and tell her to call the police if she doesn't call back, because she may not want to answer the phone and WeChat doesn't want to call back. Tell her the seriousness of the matter, ask her to call back quickly, confirm the safety through video chat, and by the way, you can transfer some money to her through WeChat to try. Maybe she'll accept it and prove that someone is there. If not, call the police and find someone.