Multiple pinned Copilot chats disappeared and continue disappearing

I've found the disappeared pinned chats at the bottom of Chats history. Then clicked on three dots -> Pin. At first, I got the error message "Couldn't pin it. Check the connection and try again". I refreshed the Copilot webpage to try again, and then the chat I tried to pin was in the Pinned section again. I head to the Copilot app to check if it appeared there as well, and it was indeed. 

All my chats have just disappeared. I had so many seriously important chats and cannot believe they've vanished from both my mobile app and the app on Windows.

I can't believe that Microsoft isn't ashamed to charge money for this. Even with Copilot Premium, chats keep disappearing completely or getting unpinned without the option to pin them back. The same thing happens in both the app and the browser. With this level of unreliability, it's unusable. I have to keep creating new chats and loading them with context and data over and over again. How many tokens are being wasted on this!

Noticed a recent chat I had pinned no longer listed as pinned. Chat disappears from History also for a time. When I locate the chat and attempt to pin, says Could not pin, check connection and try again. 
I was using browser version and switched to desktop version but issue persists on both platforms.

The same happened to me this weekend. I opened Copilot only to find that half of my pinned chats were missing. I asked Copilot if it still had access to those chats, and it said yes, so I assumed it was an indexing problem, meaning the chats were only "invisible" but still registered in the app's memory. I managed to solve the problem by opening the app in other browsers and on other platforms, such as my phone. The missing chats appeared normally in those places, and after returning to the app or the original browser and refreshing the page, they reappeared as if nothing had happened.

I deleted old conversation and find my missing chats in unpinned category. Have error message - Couldn't pin it. Check the connection and try again.

Same for me: in web version lost 2 pinned chats and I have only one account on one browser.

Pinned chats disappearing too is particularly frustrating, but pinning isn’t a separate backup. Support mentioning possible sync or indexing problems isn’t confirmation of a specific incident, and I can’t confirm a recovery method for this.

Since you’ve already checked the account, the next useful test is whether the missing chats appear in Copilot on the web versus the app. If they’re missing in both, that makes a local display/cache problem less likely. Also try any direct conversation links saved in your browser history; a chat might still open even if it’s absent from the history list.

Reply to the existing support case with a few examples: approximate chat titles, dates, when each disappeared, and whether it happens on both web and app. Ask whether the case can be escalated for account-specific chat-history investigation, and request an incident number if they believe it’s a known service issue. A community moderator may help route it, but the forum itself can’t restore account data.

Save copies of the important conversations that remain. Don’t clear your chat history or account data while investigating, and avoid posting private conversation links or content publicly.