Hi 8DWDW8,
Please note that, by default, all SharePoint site collections that are part of an Office 365 Group have the sharing setting set to Allow sharing only with the external users that already exist in your organization’s directory. To change this setting, you can use the Set-SPOSite Windows PowerShell cmdlet.
Set-SPOSite -Identity https://contoso.sharepoint.com/sites/site1-SharingCapability ExternalUserAndGuestSharing
Note: Before you run the cmdlet, please make sure the sharing settings in the SharePoint admin center has been set to "Allow sharing to authenticated external users and using anonymous access links".
Moreover, you can refer to the following article to install and connect to SharePoint Online PowerShell:
Connect to SharePoint Online PowerShell
If that doesn’t help, please share the detailed steps about how you reproduced the issue and provide a screenshot of the issue symptom.
Thanks,
Felix
