Login to Office365 Admin Portal
Portal.office365.com – https://admin.microsoft.com/
In Microsoft 365 Admin Center
Go to Setting
Under Service – Go to Office 365 Groups for Manage external sharing
Click Office 365 groups
Now here make sure the first & Second options “Let group members outside your organization access group content” is selected.
Else external / Guest users wont be able to access group content.
“Let group owners add people outside your organization” to groups is selected.
Else Team Owners wont be able to add guests
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