New Copilot update has made a chat inaccessible

I am experiencing an issue with a Copilot chat that appears to have become inaccessible after a recent update where the . This happened since Friday 21st August.

I first noticed when all of my chats were migrated except one chat which is no longer visible in my chat history. I am logged into the same Microsoft account for the chat that is missing on which I created it. I have tried searching for it on the desktop app and in the browser with no luck.

By some chance I had a Chrome browser tab open from an older Copilot session, which shows the older Copilot UI and the chat is there. The chat is fully functional: I can open it, view its history, send new messages, and receive responses. But this chat only is visible in the old UI and cannot be accessed in the new Copilot experience. The URL cannot be copied and pasted into a new tab because it redirects the copilot.microsoft.com URL to copilot.com and goes to a blank chat.

The problem is if I close this browser tab, it will not be visible anymore. I have tried on the desktop app, a fresh browser tab, a fresh browser using incognito mode and even on mobile and on all of those, the new Copilot UI/Experience loads up without the chat I need.

As part of my troubleshooting on the old Copilot Experience, I moved the chat to a "Project". But now I am unable to move it out of the "Project"

And the new Copilot experience doesn't have a "Projects" section but instead a "Notebooks" section and I can't find it there either. You can see in both screenshots the UI is different.

Because the chat now is in a Project it has a URL in the format: https://copilot.microsoft.com/projects/{project-id}/chats/{chat-id}

Opening this URL on other devices or browsers redirects to the new Copilot experience and starts a new chat instead of opening the existing Project chat.

As mentioned before on the new Copilot experience, this chat cannot be found anywhere else, even in the list "Chats".

I can confirm that this is the same Microsoft account since my other chats have synced correctly. I have tested the URL on other browsers too with the redirect issue. The Project chat remains accessible and functional only within the old Copilot session.

The chat I need contains an active, ongoing project. Although it remains accessible in the current browser tab, I have no reliable way to reopen it elsewhere, and I am concerned that if the session is lost or if I have to restart my browser or PC, I may permanently lose access to the Project chat and its accumulated context.

Could you please investigate whether this Project chat is associated with an older Copilot experience, a migration issue, or a synchronisation problem between Project chats and the newer Copilot interface?

Thanks,

J