Auto-Number Error - Number cannot be empty when creating a new item

Hi all,

I have gone through the Acumatica training material a few times on this but cannot find the issue. 

I have created a new screen with the corresponding DACs’ as per the T210 and T220 training material. I have setup the entire DAC with a master-detail relationship setup but get the following error when trying to create a new item.

Error: Inserting  'LTFGItems' record raised at least one error. Please review the errors. Error: 'Batch Nbr' cannot be empty.

This is what the screen looks like:

The DACs’ are setup with the LTFGHeader (Parent) and LTFGItems (Child) - I have just added the fields in question for the sake of saving space:

 LTFGHeader

#region BatchNbr
         PXDBString(15, IsUnicode = true, IsKey = true, InputMask = "")]
        =PXUIField(DisplayName = "Batch Number", 

Required = true, 

Visibility = PXUIVisibility.SelectorVisible)]
        tPXDefault]
        >AutoNumber(typeof(INSetupExt.usrFinGoodsBatchNbr), typeof(LTFGHeader.batchDate))]
        tPXSelector(typeof(Search<LTFGHeader.batchNbr>))]
        public virtual string BatchNbr { get; set; }
        public abstract class batchNbr : PX.Data.BQL.BqlString.Field<batchNbr> { }
        #endregion

 LTFGItem

        #region BatchNbr
                 PXUIField(DisplayName = "Batch Nbr")]
        ePXDBDefault(typeof(LTFGHeader.batchNbr))]
        FPXParent(typeof(SelectFrom<LTFGHeader>.

        Where<LTFGHeader.batchNbr.IsEqual<LTFGItems.batchNbr.FromCurrent>>))]
        public virtual string BatchNbr { get; set; }
        public abstract class batchNbr : PX.Data.BQL.BqlString.Field<batchNbr> { }
        #endregion

 

When I do not enter a Item and just save the header, it works perfectly and a new number is generated. 

 

Any help, advice or comments will be greatly appreciated. 

Thanks