Recently we came across an end-user problem where we couldn’t find our Teams in the list of Groups in Outlook Online. Making it unable to open for example the shared calendar of that Team.
Based on customer feedback, Microsoft started to roll this functionality out to Office 365 around 5-6 months ago. Old Teams are still shown, new Teams will not be shown in Outlook.
Office 365 Groups created from Microsoft Teams will be hidden from Outlook by default Based on customer feedback, new Office 365 Groups generated as a result of creating a team in Microsoft Teams will no longer show in Outlook by default. For customers that want to continue with the existing behavior of showing these groups in Outlook, an Exchange Online PowerShell cmdlet will be provided which can enable the group for the Outlook experience. Groups created through Outlook and then later enabled for Teams will continue to show in both Outlook and Teams. This update will gradually roll out across Outlook and Teams in the coming months.
Luckily, Microsoft provided a PowerShell cmdlet in order to make it visible again in Outlook Online and the Outlook client.
Set-UnifiedGroup -Identity "[name of Group/Team]" -HiddenFromExchangeClientsEnabled:$false