If you're a Microsoft Teams administrator and your users aren't able to install the Teams Meeting add-in for Outlook, schedule Outlook meetings from Teams, or schedule Teams meetings from Outlook, try the following steps to troubleshoot and resolve the issue.
If you're an administrator, you can use the diagnostic tool to validate that a user has the correct policies to enable the Teams Outlook add-in.
In the Username or Email field under Run diagnostic, enter the email address of the user who is experiencing issues when they try to enable the Teams Outlook add-in. Then, select Run Tests.
The tests will return the best next steps to resolve any tenant or policy configuration issues and validate that the user is correctly configured to enable the Teams Outlook add-in.
You can also try assigning a Teams license to the shared mailbox to see if the issue is resolved.
In some scenarios, you might not be able to access the meeting options for a meeting that's scheduled by using the shared mailbox. In this case, a workaround is to remove the shared mailbox and then add it again by using the File > Add Account option in Outlook.
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