Chat history in Messenger can be saved up to 12 months. Here are the reasons that may cause chat message missing:
1. Whether you checked in the same account;
2. Whether the seller withdrew the message;
3. If you talked with sellers at PC but cannot find the chat history at APP mobile, check whether you’ve set up “Save recent messages to TradeManager server” at PC.
If still not works, please contact Alibaba.com Customer Service for help.