Hello, Bevin: A couple of suggestions: have you enabled the Guest access in the Teams Admin Center? And the full email address of the user when you add him/her as guest? Sometimes the network traffic may cause this issue, so you can try to temporarily disable the guest access option from the Teams Admin Center, and wait for some time to re-enable it to see if the issue disappears. By the way, if you are using Teams desktop app to add the guest, please try to sign into the teams web app ( https://teams.microsoft.com/ ) and see if you can add the guest there. If the suggestions above don’t work, please provide the following information for further investigation at answers.microsoft.com 1. Please take a full screenshot about how you set up the guest access in the admin center. 2. Please take a screenshot about the error message you received when you added the guest We hope this resolves the issue.
