Power BI Embedded RLS won't work

Hi,

I am having issues testing out a solution for a client, who needs RLS. I followed GuyInACube's documentation, but when running the sample app (App owns data) all I get is 401 Unauthorized. As you can see, I have intentionally coded the username below to match a specific ID.

var generateTokenRequestParameters = new GenerateTokenRequest(accessLevel: "View",
                    identities: new List<EffectiveIdentity> { new EffectiveIdentity(username: "411FF129-8FFF-452B-AD1F-9DEDD336EA62", roles: new List<string> { "Test" },
                    datasets: new List<string> { "5e6881e9-e4bb-4eda-868f-2db80699f71c/datasets/744b301e-9140-4b8d-9310-0094c4dcd0ca" }) });

According to error prompt, I get an error on line 84:

var tokenResponse = await client.Reports.GenerateTokenInGroupAsync("groupId", "reportId", generateTokenRequestParameters);

I am currently testing this out without Premium, locally. Does this have anything to do with it - is Premium required to test RLS?

Thanks