API call for Users/<userid>/OnlineMeetings/getAllTranscripts results in 500 Internal Error

Discussed in https://github.com/microsoftgraph/msgraph-sdk-dotnet/discussions/2808

^{Originally posted by xtophs January 25, 2025}
I'm calling

var scopes = new[] { "https://graph.microsoft.com/.default" };
var authProvider = new AzureIdentityAuthenticationProvider(clientSecretCredential, null, null, scopes);

GraphServiceClient graphClient = new GraphServiceClient(httpClient, authProvider);

var transcripts = await graphClient.Users[userId].OnlineMeetings.GetAllTranscriptsmeetingOrganizerUserIdMeetingOrganizerUserIdWithStartDateTimeWithEndDateTime
  .GetAsGetAllTranscriptsmeetingOrganizerUserIdMeetingOrganizerUserIdWithStartDateTimeWithEndDateTimeGetResponseAsync( (config) =>
  {
      config.QueryParameters.StartDateTime = DateTimeOffset.Parse("2024-09-01T00:00:00Z");
      config.QueryParameters.EndDateTime = DateTimeOffset.Parse("2024-09-30T23:59:59Z");
      config.QueryParameters.MeetingOrganizerUserId = userId;
  });

to get transcripts for a user.

The Service Principal should have sufficient permissions to execute:

The SDK translates the call to

https://graph.microsoft.com/v1.0/users/<userId>/onlineMeetings/getAllTranscripts(meetingOrganizerUserId='@meetingOrganizerUserId',startDateTime=@startDateTime,endDateTime=@endDateTime)?endDateTime=2024-09-30T23%3A59%3A59.0000000%2B00%3A00&meetingOrganizerUserId=<userId>&startDateTime=2024-09-01T00%3A00%3A00.0000000%2B00%3A00

which results in a
500 Internal Server Error - Failed to Execute the Request

No further details are provided about the nature of the error.

What else is needed for the call to succeed?

Start with the C# GraphServiceClient call and compare its generated request with the documented Users//OnlineMeetings/getAllTranscripts endpoint. Reproduce the request using the supplied dates, organizer ID, and service-principal permissions, then determine whether the SDK request or Graph API requirements cause the 500; done means the call succeeds or the missing requirement is documented.