Value cannot be null.

at System.Threading.Monitor.Enter(Object obj) at System.Net.Http.Headers.HttpHeaders.ParseRawHeaderValues(String name, HeaderStoreItemInfo info, Boolean removeEmptyHeader) at System.Net.Http.Headers.HttpHeaders.AddHeaders(HttpHeaders sourceHeaders) at System.Net.Http.Headers.HttpRequestHeaders.AddHeaders(HttpHeaders sourceHeaders) at System.Net.Http.HttpClient.PrepareRequestMessage(HttpRequestMessage request) at System.Net.Http.HttpClient.SendAsync(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationToken cancellationToken) at System.Net.Http.HttpClient.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.HttpClient.PostAsync(Uri requestUri, HttpContent content, CancellationToken cancellationToken) at EPiServer.Profiles.Client.ProfileTrackingAdapter.<PostTrackingData>d__11.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at EPiServer.Profiles.Client.ProfileTrackingAdapter.<Track>d__9`1.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at EPiServer.Tracking.Core.DefaultTrackingService.<TrackAsync>d__7`1.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Epicor.Web.Business.PageViewTracker.<Track>d__6.MoveNext() in D:\a\1\s\Epicor.Web\Business\PageViewTracker.cs:line 82 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Epicor.Web.Controllers.NRArticlePageController.<Index>d__3.MoveNext() in D:\a\1\s\Epicor.Web\Controllers\NRArticlePageController.cs:line 37