Automated Warehouse Operations Engine trying to create new screen from scratch

I am trying to create an AWOE screen from scratch and have extended the ScanHeader to include the fields I need.   

simplified I have this (I have tried WMSScanHeader, QtyScanHeader, ScanHeader also) : 

 public sealed class TestingScanHeader : PXCacheExtension<ScanHeader>
 {

#region HdrOrderType
[PXDBString(2, IsKey = true, IsFixed = true, InputMask = "")]
[PXUIField(DisplayName = "Order Type")]
[PXSelector(
    typeof(Search<AMOrderType.orderType>),
    SubstituteKey = typeof(AMOrderType.orderType),
    DescriptionField = typeof(AMOrderType.descr))]
[PXDefault("RO")]  // Set default value to "RO"
public string HdrOrderType { get; set; }
public abstract class hdrOrderType : PX.Data.BQL.BqlString.Field<hdrOrderType> { }
#endregion

#region HdrProdOrdID
[PXDBString(19, IsKey = true, IsUnicode = true, InputMask = "")]
[PXUIField(DisplayName = "Prod Ord ID")]
[PXSelector(
    typeof(Search<AMProdItem.prodOrdID,
           Where<AMProdItem.statusID, In3<PX.Objects.AM.Attributes.ProductionOrderStatus.inProcess, PX.Objects.AM.Attributes.ProductionOrderStatus.released>>>),
    SubstituteKey = typeof(AMProdItem.prodOrdID),
    DescriptionField = typeof(AMProdItem.descr))]
public string HdrProdOrdID { get; set; }
public abstract class hdrProdOrdID : PX.Data.BQL.BqlString.Field<hdrProdOrdID> { }
#endregion

#region HdrEmployeeID
[PXInt()]
[PXUIField(DisplayName = "Employee ID")]
[PX.Objects.AM.Attributes.ProductionEmployeeSelector]
public int? HdrEmployeeID { get; set; }
public abstract class hdrEmployeeID : PX.Data.BQL.BqlInt.Field<hdrEmployeeID> { }
#endregion

#region EmployeeAcctCD
[PXString(30)]
[PXUIField(DisplayName = "Employee AcctCD")]
public string EmployeeAcctCD { get; set; }
public abstract class employeeAcctCD : PX.Data.BQL.BqlString.Field<employeeAcctCD> { }
#endregion

#region DefaultInventoryID
[PXInt()]
[PXUIField(DisplayName = "Dflt Inventory ID")]
[PXSelector(
    typeof(Search<InventoryItem.inventoryID>),
    SubstituteKey = typeof(InventoryItem.inventoryCD),
    DescriptionField = typeof(InventoryItem.descr))]
public int? DefaultInventoryID { get; set; }
public abstract class defaultInventoryID : PX.Data.BQL.BqlInt.Field<defaultInventoryID> { }
#endregion
}

When I try to load the screen I get this: 

Line 969:				{
Line 970:					PXDataSource datasource = ((PXPage)this.Page).DefaultDataSource;
Line 971:					if (datasource != null && PX.Data.Process.PXAuditHelper.IsInfoAvailable(datasource.DataGraph, datasource.PrimaryView))
Line 972:					{
Line 973:						PXCache cache = datasource.DataGraph.Views[datasource.PrimaryView].Cache;

Source File: C:\Program Files\Acumatica ERP\EdgemateDB\Controls\PageTitle.ascx.cs    Line: 971

Stack Trace:
 

[NullReferenceException: Object reference not set to an instance of an object.]
   PX.Data.PXGraph.CreateInstance(Type graphType, String prefix) in C:\build\code_repo\NetTools\PX.Data\Graph\Graph.cs:290
   PX.Web.UI.PXBaseDataSource.CreateDataGraphAsSingleton(Type type) +530
   PX.Web.UI.PXBaseDataSource.CreateDataGraph(Type type) +153
   PX.Web.UI.PXBaseDataSource.get_DataGraph() +415
   User_PageTitle.InitAuditMenu() in C:\Program Files\Acumatica ERP\EdgemateDB\Controls\PageTitle.ascx.cs:971
   User_PageTitle.Page_InitComplete(Object sender, EventArgs e) in C:\Program Files\Acumatica ERP\EdgemateDB\Controls\PageTitle.ascx.cs:318
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.Page.OnInitComplete(EventArgs e) +138
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2198

Basically it says that the primaryview is not initialized.  The primary veiw is the HeaderView which is 

 public PXFilter<PX.BarcodeProcessing.ScanHeader> HeaderView;

(my extension extends ScanHeader).  

If I change TestingScanHeader to a DAC that points at a table, (inherits from PXBqlTable, IBqlTable) it works and the screen loads.  But I need my HeaderView to point at an extended ScanHeader.  Any thoughts would be super thanks.