Chats disappearing and conversations getting scrambled after new Copilot update

i have reached a point where it's totally unworkable for me.  but my compagny does not allow aother ai's. 

I have an open case with Microsoft Support, and it remains active. Microsoft confirmed that this is an ongoing service-related issue affecting multiple users. They advised that a permanent fix requires backend changes, but I continue to experience these issues and have not yet received confirmation that a fix has been deployed.

Refreshing the page has occasionally brought missing messages back in my case. I have also had somewhat better results by keeping only one Copilot session active and signing out before switching browsers or computers.

I would also avoid switching browser tabs during an active Copilot conversation whenever possible. In my testing, switching tabs has repeatedly caused recent Copilot messages to disappear. However, these are only observations and temporary workarounds, not confirmed solutions. The problem has also occurred without a tab switch.

I recommend taking screenshots of important responses immediately because messages may disappear and sometimes reappear later. Unfortunately, the issue remains unpredictable.

I wanted to post this because I was looking for a solution and found this thread. I am experiencing a very similar issue with Microsoft 365 Copilot using a work account.

In my case, completed responses can disappear after I switch tabs, leave Copilot, and return. Sometimes they later reappear, but not consistently. I have also found older conversations that are now incomplete. I have reproduced the problem across different browsers, Incognito/InPrivate, a mobile phone, and another computer/network, so I opened a Microsoft support case.

During my most recent call, the support engineer told me that a data file intended to enhance Copilot search had become corrupted and was causing an “overlap” affecting search history and search results. I was told that Microsoft is working on the backend issue and rolling out an update, which may take some time. I was also told that this is a known issue affecting multiple users and that an internal service-health investigation is underway, although it is not currently visible as a public service-health notice. 

I have asked Microsoft to keep my support case open and provide updates. We’ll see. If I receive written confirmation or other meaningful information I can share publicly, I will update this thread.

Hopefully this helps others dealing with the same problem.

For the conversations that are still visible, you can preserve them without taking hundreds of screenshots. Open each important chat in Microsoft Edge, expand any collapsed sections, press Ctrl+P, and choose Microsoft Print to PDF. Save one PDF per conversation with the chat title and date. For content you still edit, paste the text into Word or OneNote and keep a second local copy.

Do not clear browser data, delete chats, or rename the affected conversations while Microsoft investigates. Make a short inventory of missing titles and note whether each was pinned, approximately when it was created, and the last time you saw the complete version. Verify that web and mobile are signed in with the exact same account address.

Then report the loss from Copilot's feedback menu and include that inventory, device/app versions, and UTC times when additional messages disappeared. The cross-device behavior points to account-side history rather than a phone cache, so preserving what remains and giving Microsoft identifiable chat details is more useful than repeatedly reinstalling the app.

Not one person has stated that they received a reply from help desk. 

Your missing and partial chats across web and mobile are consistent with the updated Copilot experience still moving account content. First confirm every device uses the identical personal account and sign-in method; Google, Apple, and Microsoft paths can represent different histories. Do not delete history while investigating. Check for an in-app link to older chats, restart Copilot, and allow time for migration to complete. Then use the Microsoft privacy dashboard to export all Copilot activity history, giving you a copy of retained prompts and responses. Signed-in conversation history is retained for 18 months, but retired Group Chat content does not carry forward after the 2026 app change. If ordinary chats remain incomplete, use Copilot’s ellipsis menu > Send feedback > Report a problem. Include when the loss began, affected chat titles, device versions, and screenshots. There is no documented client-side restoration tool, so Microsoft must investigate persistent server-side loss.