Unable to update the changes using OData Service with DXA & XPM

Question

While using XPM everything seems to work correctly, except when it comes to update preview.

When I try to update preview I see the error

Unable to update the changes using OData Service. The remote server returned an error: (406) Not Acceptable.

Looking at the Event Viewer I see more information

Unable to update the changes using OData Service. The remote server returned an error: (406) Not Acceptable.

Component: Tridion.ContentManager.Publishing.PreviewService Errorcode: 1003 User: NT AUTHORITY\NETWORK SERVICE

StackTrace Information Details: at System.Net.HttpWebRequest.GetResponse() at System.Data.Services.Client.DataServiceContext.SaveResult.BatchRequest(Boolean replaceOnUpdate) at System.Data.Services.Client.DataServiceContext.SaveChanges(SaveChangesOptions options) at Tridion.ContentManager.Publishing.PreviewService.ServiceImplementation.Preview(IEnumerable1 publishedItemsInfo, TcmUri publishingTargetId) at Tridion.ContentManager.Publishing.PreviewService.ServiceImplementation.Preview(IEnumerable1 publishedItemsInfo, TcmUri publishingTargetId) at Tridion.ContentManager.Publishing.PreviewService.FastTrackPublishingService.Preview(IEnumerable`1 publishedItemsInfo, TcmUri publishingTargetId) at SyncInvokePreview(Object , Object[] , Object[] ) at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs) at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc) at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

However I do not see anything meaningful in any of the Discovery logs, SE logs or CME logs (all in DEBUG mode).

I've followed the guide here, http://docs.sdl.com/LiveContent/content/en-US/SDL%20Web-v1/GUID-80AD06B5-DB74-4AE8-9934-4BA8BC1C6D51, to turn off oauth authentication but I am still seeing the issue.

I assume it has to do with the setting on the Publication Target (yes, using legacy) but I am unable to determine what. Below are the settings in my staging target

Answer 1

406 happens when the server cannot respond with the accept-header specified in the request, so this definitely is a configuration issue.

As mentioned in the documentation (http://docs.sdl.com/LiveContent/content/en-US/SDL%20Web-v1/GUID-6A8C7A13-A652-4134-B93E-9AFED1A7DC22) you should set the Content Delivery Endpoint URL to the URL of the Experience Manager Web service end point.

You appear to be using the Content service while you should be using the Session-enabled Content service in this case, see http://docs.sdl.com/LiveContent/content/en-US/SDL%20Web-v1/GUID-B392E30C-7A2D-4C8F-80E3-43B29F5F891B