Create Parallel Tests with 3rd party cloud host in C#

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Has anyone tried this with Browserstack I am unable to perform it after looking through the documentation.
I created an app.config:







I created a Parallels class
class iParallel
{
protected IOSDriver _IOSdriver;
[TestFixture]
[TestFixture(“parallel”, “iPhone XR”)]
[TestFixture(“parallel”, “iPhone 11”)]
//[TestFixture(“parallel”, “iPhone 8”)]

    [Parallelizable(ParallelScope.Fixtures)]
    public class ParallelTest : BrowserStackNUnitTest
    {

        public ParallelTest(string profile, string device) : base(profile, device) { }
    }

I have a BrowserstackNUnitTest class and use: AppiumOptions opt = new AppiumOptions();

        foreach (string key in caps.AllKeys)
            {
            opt.AddAdditionalCapability(key, caps[key]);
            }

            foreach (string key in devices.AllKeys)
            {
            opt.AddAdditionalCapability(key, devices[key]);
            }

            String username = Environment.GetEnvironmentVariable("BROWSERSTACK_USERNAME");
            if (username == null)
            {
                username = ConfigurationManager.AppSettings.Get("user");
            }

            String accesskey = Environment.GetEnvironmentVariable("BROWSERSTACK_ACCESS_KEY");
            if (accesskey == null)
            {
                accesskey = ConfigurationManager.AppSettings.Get("key");
            }

        opt.AddAdditionalCapability("browserstack.user", username);
        opt.AddAdditionalCapability("browserstack.key", accesskey);

            String appId = Environment.GetEnvironmentVariable("BROWSERSTACK_APP_ID");
            if (appId != null)
            {
            opt.AddAdditionalCapability("app", appId);
            }
        
        // _IOSdriver = new IOSDriver<IOSElement>(new Uri("http://" + ConfigurationManager.AppSettings.Get("server") + "/wd/hub/"), capability);
        Uri uri = new Uri("http://" + ConfigurationManager.AppSettings.Get("server") + "/wd/hub/");
           _IOSdriver = new IOSDriver<IOSElement>(uri, opt);

When running this I get System.nullReferenceException: object reference not set to an instance of an object.