Can't Query Google Analytics Reports API Using OAuth 2

I am trying to to use the latest version of the Report API using OAuth 2. It doesn't appear that there are many people using this version yet, so it has been really hard to find examples.

I have a refresh token, which I am using to generate an access token.

private AnalyticsService getAnalyticsService()
{
    AuthorizationServerDescription description = new AuthorizationServerDescription();
    description.TokenEndpoint = new Uri(login.TokenEndpoint);
    description.AuthorizationEndpoint = new Uri(login.AuthorizationEndpoint);
    WebServerClient client = new WebServerClient(description, login.ClientId, login.ClientSecret);

    OAuth2Authenticator<WebServerClient> authenticator = new OAuth2Authenticator<WebServerClient>(client, authenticate);
    AnalyticsService service = new AnalyticsService(authenticator);
    return service;
}

private IAuthorizationState authenticate(WebServerClient client)
{
    string[] scopes = new string[] { login.ScopeUrl }; // not sure if this is necessary
    IAuthorizationState state = new AuthorizationState(scopes) { RefreshToken = login.RefreshToken };

    client.RefreshToken(state);
    return state;
}

This appears to be working just fine:

{
 "access_token" : "ya29.AHES6ZQy67SSLHWJWGWcLbLn69yKfq59y6dTHDf4ZoH9vHY",
 "token_type" : "Bearer",
 "expires_in" : 3600
}

However, when I do a request, I am getting an error. For example, here is a query that results in an error:

AnalyticsService service = getAnalyticsService();
ManagementResource.ProfilesResource.ListRequest request = service.Management.Profiles.List("~all", "~all");
return request.Fetch();

This is the error I get:

{"error":{"errors":[{"domain":"global","reason":"authError","message":"Invalid
Credentials","locationType":"header","location":"Authorization"}],"code":401,"message":"Invalid
Credentials"}}

I have tried other queries, providing valid profile IDs. However, I am always getting a 401 error, saying I'm not authorized. I am having trouble finding examples where people are using this code. It could be something simple like a bad URL or something. Unfortunately, I have no way to telling. It seems strange that I can get an access token, but I can't seem to perform any queries.