Power bi Dashboard embeded

Hi,

After following https://github.com/Microsoft/PowerBI-Developer-Samples/tree/master/App%20Owns%20Data

this tutorial i was am to embed my given report without problem.

However (using the same configuration), i failed to perform dashboard and tiles embed and got the below error instead.

Operation returned an invalid status code 'InternalServerError'

Which was thrown on this code segment

var tokenResponse =
await client.Dashboards.GenerateTokenInGroupAsync(GroupId, dashboard.Id,
generateTokenRequestParameters);

Is there anything special that needs to be handle for Dashboard and tiles embedding 

Regards,

Eng