Using Call Back on backend (401 - 40100 error received)

From @pLopezFr on Twitter who tweets:

“Is there any doc on how to use "Azure Callback" in the backend ? All I can get is 401-40100 Unauthorized Send”

When engaged the customer also added: “Hi. Here is my error message :401 - 40100: Unauthorized : Unauthorized access for 'Send' operation on endpoint 'sb”.

“I'm using Iiothubowner connexion string. iothubowner has all rights on the hub”

Tweet URL: https://twitter.com/plopezFr/status/695203299369312256 and DM
 
Thanks,
@AzureSupport