PowerBIClient.Datasets.GetGatewayDatasourcesAsync returns NULL

Hi,

I am trying to embed Power BI reports (using Direct Query) in my ASP.NET application, and get "Can't display the visual" message. I understand that I need to patch my data source credentials.

I am using this sample to provision my workspace, import reports, etc. Everything works great, except option #7 "Update connection string info for an existing dataset". Line 544 returns NULL into datasources variable, even though all three parameters are correct:

// Get the datasources from the dataset
var datasources = await client.Datasets.GetGatewayDatasourcesAsync(workspaceCollectionName, workspaceId, datasets.Value[datasets.Value.Count - 1].Id);

Any ideas what could be the problem?

Thanks,

Julia