One of my user not able to chat with another user.

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Hello @Reeshma Arun

I would like to first clarify that this is a user‑to‑user support forum. Moderators here are not Microsoft Support, so we don’t have backend access or the ability to perform escalations.

From my experience, this can happen when Teams detects multiple chat threads with the same user and is trying to consolidate the conversations. In some cases, the original chat thread may become inaccessible, or users may experience unexpected behavior when sending messages. Could you please confirm:

• Is the issue affecting only these two users, or can either user chat with other people normally?
• What happens when the user clicks Switch chat?
• Are both users in the same organization, or is one an external/guest user?
• Does the issue occur in both the Teams desktop client and Teams on the web (Teams on the web)?
• Is the affected device running Windows or macOS?
• Have you already tried clearing the Teams cache on the affected device?

If you are a Microsoft 365 administrator, could you also check whether the user L has any duplicate accounts (for example, multiple Entra ID/Azure AD objects with similar sign-in information)? Duplicate accounts can sometimes lead to unexpected chat behavior.

Looking forward to your reply.

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