Embedded paginated report with PowerBI dataset

I am getting bad request on this, I can't spot any deviation from the working example.

The effective identity contains the reportId, datasetId and username. 

Any ideas? 

AmosHersch 

                var reports = new List<GenerateTokenRequestV2Report>() { new GenerateTokenRequestV2Report(report.Id) };
                var datasets = new List<GenerateTokenRequestV2Dataset>() { new GenerateTokenRequestV2Dataset(datasetId, XmlaPermissions.ReadOnly) };
                var workspaces = new List<GenerateTokenRequestV2TargetWorkspace>() { new GenerateTokenRequestV2TargetWorkspace(groupId) };
                var identities = new List<EffectiveIdentity>() { effectiveIdentity };

                var tokenRequest = new GenerateTokenRequestV2(datasets, reports, workspaces, identities);
                var embedToken = client.EmbedToken.GenerateToken(tokenRequest);

                return embedToken;