Copilot Disappeared from Outlook: It's Not a Feature but a Bug. Microsoft Fixes It

Microsoft has resolved a malfunction that, in recent weeks, caused the Copilot Chat buttons to disappear from classic Outlook on Windows. The issue affected only users with a Copilot Chat (Basic) license, while those with a paid subscription to Microsoft 365 Copilot did not encounter any anomalies.

The defect appeared after the Outlook update to build 20026.20182 or later. From that moment, several users reported the sudden disappearance of access points to Copilot within the classic desktop client. The Copilot button could disappear from the upper right area above the ribbon. In some cases, the icon was also missing from the app sidebar or the Other apps section. Those searching for Copilot in the Add app section found it listed, but the Open button had no effect. Even attempting to reinsert the command via ribbon customization often resulted in an unavailable or disabled icon.

Fortunately, Copilot remained accessible through other channels, such as Outlook on the web and the standalone app or web version of Microsoft 365 Copilot. This detail limited the practical impact of the bug but did not quell the complaints from those who work daily from the desktop client.

Microsoft has confirmed the resolution of the problem through a service-side modification applied on June 29, 2026, by the Outlook team. Those who still do not see the buttons restored are advised to restart the application to force the download of the change. The company also recommends updating to the latest available build, while for those who cannot proceed with the update right away, some temporary solutions remain available: switching to New Outlook, using Outlook Web Access, or reverting to the previous build 16.0.20026.20168 for Current Channel users, which predates the bug's appearance.

However, Microsoft warns that the rollback should only be considered a temporary remedy. Disabling Office updates to remain on an older build indeed exposes users to the risk of losing future security fixes; therefore, the recommendation is to reactivate them as soon as possible.

In the meantime, the company is investigating another known issue, this time related to sudden Outlook crashes on systems with Kaspersky Antivirus installed, linked to the Mail Checker component (mcou.dll). Users experiencing crashes are encouraged to check the application log for events 1000 with OUTLOOK.EXE as the application and MCOU.DLL as the responsible module, and to contact Kaspersky support directly if confirmed.

In recent months, Microsoft has already addressed two similar defects: one that prevented sending emails via Outlook.com from the classic client, and the other that rendered Outlook unusable for those who had enabled the Microsoft Teams Meeting add-in.