Operation returned an Invalid status code 'Unauthorized' (User owns data)

All,

I'm stuck in calling the PowerBi API from my project. What I did was create a MVC application, login with AzureId for the whole site, get a token for PowerBi and get a report. All goes well, except the retrievel of the report. No matter what call I do to the PowerBi Client, if only gives me Unauthorized. 

When I try the same for https://docs.microsoft.com/nl-nl/rest/api/power-bi/reports/getreports#code-try-0 It all goes well, so the user who logges in is not the problem.

When I go back to my app and look at the token (via https://jwt.io/), I also think I have the correct permissions, which are set in the Azure portal:

"scp": "App.Read.All Capacity.Read.All Capacity.ReadWrite.All Content.Create Dashboard.Read.All Dashboard.ReadWrite.All Data.Alter_Any Dataflow.Read.All Dataflow.ReadWrite.All Dataset.Read.All Dataset.ReadWrite.All Gateway.Read.All Gateway.ReadWrite.All Group.Read Group.Read.All Metadata.View_Any Report.Read.All Report.ReadWrite.All StorageAccount.Read.All StorageAccount.ReadWrite.All Tenant.Read.All Tenant.ReadWrite.All Workspace.Read.All Workspace.ReadWrite.All",

No matter what call I make to the Api, all calls are Unauthorized  (the calls below are all I tried)

var tokenCredentials = new TokenCredentials(Request.Cookies["token"].ToString(), "Bearer");
using (var client = new PowerBIClient(new Uri(ApiUrl), tokenCredentials))
{
	var groupid = new Guid("guid of the group");
	var a = client.Reports.GetReportsInGroup(groupid);
	var x = client.Groups.GetGroups();
	var r1 = client.Reports.GetReports();
}

Does anyone have a clue what I'm doing wrong?

In addition the following lines generate an authorization code and access_code when not yet available:

public void GetAuthorizationCode()
{
	var @params = new NameValueCollection
	{ {"response_type", "code"},
		{ "client_id", ClientID},
		{ "resource", "https://analysis.windows.net/powerbi/api"},
		{ "redirect_uri", RedirectURL} };

	var queryString = HttpUtility.ParseQueryString(string.Empty);
	queryString.Add(@params);

	string strUrl = $"https://login.windows.net/common/oauth2/authorize?{queryString}";

	Response.Redirect(strUrl);
}

public async Task<string> GetAccessToken(string authorizationCode, string clientID, string clientSecret, string redirectUri)
{
	TokenCache TC = new TokenCache();

	string authority = "https://login.microsoftonline.com/common";
	AuthenticationContext AC = new AuthenticationContext(authority, TC);
	ClientCredential cc = new ClientCredential(clientID, clientSecret);

	AuthenticationResult result = await AC.AcquireTokenByAuthorizationCodeAsync(authorizationCode, new Uri(redirectUri), cc);



	return result.AccessToken;
}