Hi VaughanPC,
This issue was posted to the Service Health Dashboard (SHD) as incident
TM149267 starting at Sep 13 2018 10:58 PM (UTC). The user experience of this incident is:
Users may be unable to add guest members to Microsoft Teams. More info: Additionally, admins may be unable to change the Guest Access option in the Microsoft Teams admin center. Specifically, the Guest Access function may appear to be working,
but the feature isn't executing the change as expected.
For affected customers to easily identify the information here, this thread will be closed. You may subscribe to the following thread for updated information:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_o365admin-mso_teams-mso_o365b/guests-not-able-to-view-team/c5f28c9b-8252-4c0b-b390-a19a6c409a94?tm=1536803774592
If you are in a different situation, please post back and let us know the detailed scenario. .
Thanks,
Carlos