Embedding - Only group admin can embed group content - AppOwnsData sample

I am trying to run the sample AppOwnsData project (https://github.com/Microsoft/PowerBI-Developer-Samples/tree/master/App%20Owns%20Data) and I have followed the directions and created a native app in Azure AD and assigned the correct permissions.

I have an error when trying to generate a token to use when embedded the report.

{ "error": { "code": "InvalidRequest", "message": "Only group admin can embed group content" }}

When I use Postman to GET GroupUsers from the service my account is listed as an Admin for the group.

https://api.powerbi.com/v1.0/myorg/groups/<workspaceid>/users

{
"@odata.context": "http://<blabla>.analysis.windows.net/v1.0/myorg/groups/<workspaceid>/$metadata#users",

"value": [
{
"emailAddress": "<my email address>",

"groupUserAccessRight": "Admin"
}
....<other people>
]
}

Any ideas what i can do so that service does not tell me "only group admin can emded content" ?

thanks

Mark.