Hi,
I get this error when using feeds in version 9.12.5 with the XML Feed Provider.
As I could read here, it seems like the input "ProductGroups" are invalid and should be removed from the feed: https://doc.dynamicweb.com/forum/pim/pim/publishing-pim-feed-raises-error 
Only problem is, that I haven't selected the property.
How do I fix this?
This is the error: 
{
  "Message": "An error has occurred.",
  "ExceptionMessage": "Some property names do not match the viewmodel ('Dynamicweb.Ecommerce.ProductCatalog.ProductListViewModel'): Invalid input=[ProductGroups], Valid property names=[Group, SubGroups, Products, PageSize, PageCount, CurrentPage, TotalProductsCount, SpellCheckerSuggestions, FacetGroups].",
  "ExceptionType": "System.ArgumentException",
  "StackTrace": "   at Dynamicweb.Ecommerce.ProductCatalog.ViewSettingsBase`1.CheckInvalidNames()\r\n   at Dynamicweb.Ecommerce.ProductCatalog.ViewSettingsBase`1.AddProperties(ICollection`1 propertyNames)\r\n   at Dynamicweb.Ecommerce.ProductCatalog.ViewSettingsBase`1.set_FilledProperties(String[] value)\r\n   at Dynamicweb.Ecommerce.Feeds.FeedProvider.CreateProductListSettings(ProductCatalogSettings settings, FeedContextConfiguration feedContextConfiguration)\r\n   at Dynamicweb.Ecommerce.Feeds.FeedProvider.GetFeedModel(Feed Feed, FeedContextConfiguration feedContextConfiguration)\r\n   at Dynamicweb.Ecommerce.Feeds.XMLProvider.GetOutput(Feed feed, FeedContextConfiguration feedContextConfiguration)\r\n   at Dynamicweb.Ecommerce.WebAPI.Controllers.FeedController.GetFeedOutput(Int32 id, FeedContextConfiguration feedContextConfiguration)\r\n   at lambda_method(Closure , Object , Object[] )\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"
}
BR 
Marie Louise