Hope you are doing well.
As per the documentation: Microsoft Graph Calendar Events API, I am able to generate the Online Teams Meeting URL successfully for the existing users. However, I am able to replicate this issue with Online Teams Meeting URL generation for the new users.
As per my analysis, reason for this issue is that teams for business meeting provider (Online Teams Meeting) is not yet enabled for the user in Outlook /Outlook Calendar. Hence allowedOnlineMeetingProviders is showing up empty data when we query using below Graph API.
GET https://graph.microsoft.com/v1.0/{id | userPrincipalName}/calendar
Example of above API response for the below two properties for the user for whom Online Teams Meeting URL is not generated:
"allowedOnlineMeetingProviders": [], "defaultOnlineMeetingProvider": "unknown",
Example of Outlook Calendar UI for this user where teams for business meeting provider (or Online Teams Meeting) is not yet enabled:
Example of Outlook Calendar UI for teams for business meeting provider (or Online Teams Meeting) enabled user :
Hence this is not the issue with Microsoft Graph API instead it seems to be the issue with Outlook /Outlook Calendar in enabling teams for business meeting provider (or Online Teams Meeting) for the new users.
I would advise you to open a support case with Graph API or Outlook Calendar team from your tenant for dedicated support and escalating it to Microsoft engineering team to analyze this issue and further assistance. You can raise the case either from Azure or M365 admin center of your tenant.
Hope this helps.
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