Why was the message history of Teams disappeared and how can I recover and let it do not?

Dear @Seongbeen Mun,

I understand how concerning it is when Teams chat history suddenly disappears.

This issue can occur for several reasons, including:

• Retention or messaging policies configured by your Microsoft 365 administrator that automatically delete older chat messages.
• Account or tenant changes, such as signing in with a different account or being moved to another tenant.
• Synchronization issues with the Teams client.
• In rare cases, a service issue or data inconsistency.

If you are an end user, could you also confirm:

• Are the missing messages from 1:1 chats, group chats, or channel conversations?
• Are they missing in both the Teams desktop app and Teams on the web?
• Is this affecting only one chat or multiple chats?

This information will help narrow down the cause.

In the meantime, to resolve the issue, I suggest the following steps:

1. Confirm you’re signed in with the correct account and organization.
2. Check Teams on the web to see if the messages are available there. If they are, the issue is likely with the desktop client cache or synchronization.
3. Ask your Microsoft 365 administrator to verify whether any retention policies have been applied that may have removed the chat history. Once messages are permanently deleted by a retention policy, they generally cannot be recovered.
4. If no retention policy is involved and the messages are missing across all Teams clients, the administrator should open a support request with Microsoft to investigate whether this is a service-side issue.

For more information, please refer to Microsoft’s documentation on retention policies for Microsoft Teams: Learn about retention for Microsoft Please let me know if you have any questions.

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