You are in the middle of a detailed conversation with Copilot in Microsoft 365 when the session stops responding. A banner appears at the top of the chat pane: Connection Lost. This error is most common in long conversations that involve multiple file uploads, complex document summaries, or iterative code generation. The root cause is a timeout in the session token or a network interruption triggered by the sheer volume of data exchanged.
This article explains why Copilot drops the connection during extended interactions and gives you a reliable sequence of steps to restore the session. You will also learn how to prevent the error by adjusting your conversation habits and checking your network configuration. The fix does not require admin privileges, but some steps depend on your Microsoft 365 license type.
Key Takeaways: Recovering from Copilot Connection Drops
- Refresh the Copilot pane (Ctrl+Shift+R): Forces a new session token without closing your Microsoft 365 app.
- Break long conversations into separate threads: Keeps each session under the token expiry limit and reduces data load.
- Check your network proxy or VPN: Proxies that inspect SSL traffic can drop long-lived WebSocket connections used by Copilot.
Why Copilot Loses Connection During Long Conversations
Copilot in Microsoft 365 uses a WebSocket connection to maintain real-time communication between your client application and Microsoft’s cloud service. Each session is authenticated with an access token that has a default lifetime of 60 minutes. In long conversations where you send multiple prompts and receive large responses, the token can expire before you finish your task. The server then sends a Connection Lost signal because the authentication context is no longer valid.
Another factor is the cumulative payload size. Every file you attach, every block of code you generate, and every long document summary adds to the session memory. When the total data exchanged exceeds a threshold that Microsoft does not publish publicly, the server terminates the connection to protect performance for other users. Network interruptions from unstable Wi-Fi, corporate proxies that inspect SSL traffic, or VPNs that time out idle connections also trigger the same error message.
Session Token Expiry
Microsoft Entra ID issues tokens that last 60 minutes by default for interactive sessions. Copilot does not refresh the token automatically while a conversation is active. If your conversation extends beyond 60 minutes, the token becomes invalid and the WebSocket closes. Refreshing the pane forces a new token request.
Data Volume Limits
Copilot has a practical limit on how much context it can hold in a single conversation. Uploading multiple large documents or copying extensive code blocks pushes the session toward this limit. When the limit is reached, the server sends a disconnect signal to prevent service degradation for other users.
Steps to Recover From a Connection Lost Error
Follow these steps in order. Do not skip the first step, because it resolves most cases without any data loss.
- Refresh the Copilot pane with Ctrl+Shift+R
Press Ctrl+Shift+R on your keyboard while the Copilot pane is open. This shortcut reloads the pane without closing your Microsoft 365 app. Copilot requests a new access token and reconnects to the server. Your conversation history up to the disconnect point is preserved in the session cache. - Copy your last prompt before refreshing
If the refresh does not restore the conversation, select the text of your last prompt and copy it to the clipboard. Then close the Copilot pane by clicking the Copilot icon in the ribbon. Reopen the pane and paste your prompt. This starts a new session with a fresh token and clears the accumulated data volume. - Sign out of Microsoft 365 and sign back in
Click your profile picture in the top-right corner of the Microsoft 365 app. Select Sign out. Wait 30 seconds, then sign in again with your work or school account. This step forces Microsoft Entra ID to issue a completely new token and resets all WebSocket connections. - Disable your VPN or proxy temporarily
If you use a corporate VPN or a web proxy, turn it off for one minute. Refresh the Copilot pane again. If the error disappears, your network equipment is interfering with the WebSocket connection. Contact your IT department to add the necessary endpoints to the allowlist. - Run the Microsoft 365 network connectivity test
Open a browser and go to connectivity.office.com. Sign in with your work account and click Run test. The tool checks whether your network can reach the Copilot service endpoints. If any test fails, share the result with your IT team.
If Copilot Still Has Issues After the Main Fix
Copilot Reconnects but Then Immediately Disconnects Again
This pattern indicates a network issue that interrupts the WebSocket repeatedly. Check your Wi-Fi signal strength or switch to a wired Ethernet connection. If you are on a corporate network, ask your IT team to verify that the following domains are not blocked or inspected: copilot.microsoft.com and all subdomains, bing.com and all subdomains, and office.com and all subdomains.
Copilot Works in a New Conversation but Not in the Original
The original conversation exceeded the data volume limit. Copilot cannot recover that session because the context is too large. Start a new conversation and break your task into smaller parts. For example, if you were summarizing a 200-page document, split it into 50-page chunks and process each chunk in a separate thread.
Connection Lost Error Appears in Every Conversation
A persistent error across all conversations points to a local client issue. Repair your Microsoft 365 installation by going to Control Panel > Programs and Features, selecting Microsoft 365, and clicking Change > Quick Repair. After the repair completes, restart your computer and test Copilot again.
Copilot Free vs Copilot for Microsoft 365: Connection Stability Comparison
| Item | Copilot Free | Copilot for Microsoft 365 |
|---|---|---|
| Session token lifetime | 60 minutes | 60 minutes |
| Data volume limit per conversation | Lower, approximately 10 prompts with attachments | Higher, approximately 30 prompts with attachments |
| Network endpoint priority | Standard consumer routing | Dedicated enterprise routing with SLA |
| Ability to resume after refresh | Partial, some context may be lost | Full, context is preserved in the cloud cache |
After completing the steps above, you can resume your work with Copilot without losing the progress you made before the error. To avoid the issue in future sessions, set a timer for 45 minutes and start a new conversation before the token expires. If you frequently handle large documents, use the Copilot for Microsoft 365 license, which offers a higher data volume limit and enterprise-grade network routing.