According to IT之家, citing a bleepingcomputer report, Microsoft has pushed a patch to classic Outlook that fixes the disappearance of Copilot Chat and the Copilot button. Microsoft had previously acknowledged that after classic Outlook was upgraded to Build 20026.20182 and later, some users with a Copilot Chat license or a paid M365 Copilot account could lose Copilot Chat and Copilot entry points, because Outlook failed to retrieve the required account information from the user profile. Affected users can run the official Copilot troubleshooting tool, tick "Show apps in Outlook" under File > Options > Advanced in the Outlook pane, or use Copilot in the new Outlook or Outlook on the web instead.