Microsoft has fixed a known issue that removed the Copilot Chat and Copilot buttons in the classic Outlook desktop mail client for some Windows users.

As explained in an updated support document, affected users with the Copilot Chat (Basic) license or a Microsoft 365 Copilot (Premium) account no longer saw Copilot buttons in the side navigation and above the ribbon.

Those impacted by this experienced one or more of the following issues:

• The Copilot button missing from the top-right area above the ribbon.
• The Copilot icon missing from the left app bar or More Apps area in classic Outlook.
• In Add Apps, Copilot may appear as an available app, but selecting Open does nothing.
• Adding Copilot through ribbon customization may show the command as unavailable or grayed out.
• Copilot remains available from other entry points, such as Outlook on the web or the Microsoft Copilot standalone app or web experience.

Microsoft first announced in June that it had fixed the bug with a service change, but last month it said it had started investigating again after recent updates caused it to resurface.

Now, Microsoft says it has finally resolved this classic Outlook issue, blaming it on a bug that prevented Outlook from retrieving some account information 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 reads.

"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 shared a temporary workaround for those still affected by this known issue, which requires enabling the "Show Apps in Outlook" option in classic Outlook settings by selecting the File tab, then going to Options > Advanced and checking the "Show Apps in Outlook" box under "Outlook panes."

Affected users can also use the new Outlook email client or Outlook Web Access (OWA), which are not affected by this bug, or create a new Outlook profile.

Since the start of the year, Microsoft has also resolved known issues that prevented some classic Outlook users from sending emails via Outlook.com and rendered the classic Outlook client unusable when enabling the Microsoft Teams Meeting Add-in.