POST Failed at Xamarin.UITest.Shared.Http.HttpClient.HandleHttpError

Hi,

I have the following error and I have no idea what it means. It does not happen in the emulator--only when it runs on a physical phone (or in appcenter with 'Test on a real device' enabled).

1) Error : AppCenter.UITest.Android.Tests.AppDoesLaunch
System.Net.WebException : POST Failed
at Xamarin.UITest.Shared.Http.HttpClient.HandleHttpError (System.String method, System.Net.Http.HttpResponseMessage response, Xamarin.UITest.Shared.Http.ExceptionPolicy exceptionPolicy) [0x00052] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Shared.Http.HttpClient.SendData (System.String endpoint, System.String method, System.Net.Http.HttpContent content, Xamarin.UITest.Shared.Http.ExceptionPolicy exceptionPolicy, System.Nullable1[T] timeOut) [0x00123] in <18ae7883e2424c558186d1d9edf9f14b>:0 at Xamarin.UITest.Shared.Http.HttpClient.Post (System.String endpoint, System.String arguments, Xamarin.UITest.Shared.Http.ExceptionPolicy exceptionPolicy, System.Nullable1[T] timeOut) [0x00014] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Shared.Android.HttpApplicationStarter.Execute (System.String intentJson) [0x00035] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Shared.Android.AndroidAppLifeCycle.LaunchApp (System.String appPackageName, Xamarin.UITest.Shared.Android.ApkFile testServerApkFile, System.Int32 testServerPort) [0x000a1] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Shared.Android.AndroidAppLifeCycle.LaunchApp (Xamarin.UITest.Shared.Android.ApkFile appApkFile, Xamarin.UITest.Shared.Android.ApkFile testServerApkFile, System.Int32 testServerPort) [0x00007] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Android.AndroidApp..ctor (Xamarin.UITest.Configuration.IAndroidAppConfiguration appConfiguration, Xamarin.UITest.Shared.Execution.IExecutor executor) [0x00193] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Android.AndroidApp..ctor (Xamarin.UITest.Configuration.IAndroidAppConfiguration appConfiguration) [0x00000] in <18ae7883e2424c558186d1d9edf9f14b>:0
at Xamarin.UITest.Configuration.AndroidAppConfigurator.StartApp (Xamarin.UITest.Configuration.AppDataMode appDataMode) [0x00017] in <18ae7883e2424c558186d1d9edf9f14b>:0
at AppCenter.UITest.Android.Tests.SetUp () [0x00010] in :0
at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
at System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00032] in <48b95f3df5804531818f80e28ec60191>:0