Microsoft has resolved a known problem that concealed the Copilot Chat and Copilot buttons in the classic Outlook desktop mail client for select Windows users.

According to an updated support document, users holding the Copilot Chat (Basic) license or a Microsoft 365 Copilot (Premium) account no longer encountered missing Copilot buttons in the side navigation and above the ribbon.

Those affected reported one or more of these symptoms:

The Copilot button absent from the top-right area above the ribbon.
The Copilot icon missing from the left app bar or More Apps section in classic Outlook.
In Add Apps, Copilot may display as available, yet selecting Open produces no response.
Adding Copilot via ribbon customization may render the command unavailable or grayed out.
Copilot stays accessible through other points, such as Outlook on the web or the Microsoft Copilot standalone app or web experience.

Microsoft initially reported fixing the bug via a service change in June, yet last month noted it had reopened the investigation after recent updates caused the issue to return.

The company now confirms the classic Outlook problem is fully resolved, attributing it to a bug that blocked Outlook from pulling certain account details from the user's Outlook profile.

"We fixed an issue in classic Outlook that could cause the Copilot entry point to be missing from the navigation pane when required account information could not be retrieved from the user's Outlook profile. The Copilot button might be missing for several different reasons, including licensing, Microsoft 365 app configuration, update channel, privacy settings, or other environmental factors," an update to the original support document states.

"Because the missing button is a symptom that can have multiple underlying causes, we recommend following the guidance in Copilot troubleshooters and How to find and enable missing Copilot button in Microsoft 365 apps to identify and resolve the issue."

Microsoft also provided a temporary workaround for users still impacted, which involves enabling the "Show Apps in Outlook" option in classic Outlook settings by selecting the File tab, then navigating to Options - Advanced and checking the "Show Apps in Outlook" box under "Outlook panes."

Affected users may also switch to the new Outlook email client or Outlook Web Access (OWA), which remain unaffected by this bug, or create a new Outlook profile.

Since the start of the year, Microsoft has likewise fixed known issues that stopped some classic Outlook users from sending emails via Outlook.com and made the classic Outlook client unusable when enabling the Microsoft Teams Meeting Add-in.