Unable to Create or Fetch Teams Online Meetings via Microsoft Graph API

I am experiencing issues with creating and fetching Teams online meetings using the Microsoft Graph API in my tenant. Despite having the proper permissions and licensing, all attempts to use the /users/{userPrincipalName}/onlineMeetings endpoint return the following errors:

• 404 - UnknownError: When trying to create or fetch meetings.

Key Details:

• Endpoints Involved:
• /users/{userPrincipalName}/onlineMeetings (POST): Used to create a new Teams online meeting for a specific user.
• /users/{userPrincipalName}/onlineMeetings (GET): Used to fetch a list of online meetings for a specific user.
• Environment:
• Affected users include valid, licensed users in my tenant (e.g., ******@mydomain.com).
• The app registration is configured with application permissions and has admin consent for OnlineMeetings.ReadWrite.All.
• What Works:
  • Users can manually create Teams meetings via the Teams client without any issues.
• What Fails:
  • Using the /onlineMeetings endpoint with correct payloads results in a 404 error.
  • The /get-meetings API also fails to fetch meetings for any user in the tenant.
• What I’ve Checked:
  • The affected users have valid Microsoft 365 Business Standard licenses, including Teams and Exchange.
  • The Global (Org-wide default) meeting policy is configured to allow scheduling meetings.
  • Permissions on the app are set to OnlineMeetings.ReadWrite.All with admin consent granted.
• Example error

     {
      "error": {
        "code": "UnknownError",
        "message": "",
        "innerError": {
          "date": "2024-12-04T19:52:32",
          "request-id": "8aa00d4f-32fe-46bb-9ec0-7788c116fd46",
          "client-request-id": "b1954318-5f0c-bb80-81b7-a7cb90e3d9cd"
        }
      }
    }
  

  Question:
  What could be causing the /onlineMeetings endpoint to fail with 404 for all users in my tenant? Are there any additional tenant or backend configurations that need to be checked to enable API-based meeting creation? Any guidance or suggestions would be greatly appreciated!