FieldUpdated Event in ARPaymentEntry Not Fetching ARRegister RefNbr by Custom Field (UsrLinksoftARInvoiceNumber)

Hi community,

I'm customizing the ARPaymentEntry screen in Acumatica and encountering an issue where a custom field update event doesn't fetch the matching RefNbr from ARRegister even though the data exists in the database.

I’ve added two custom fields using DAC extensions:

public class ARRegisterExt : PXCacheExtension<PX.Objects.AR.ARRegister>
 {    

     #region UsrLinksoftARInvoiceNumber
     [PXDBString(50)]
     [PXUIField(DisplayName = "Linksoft AR Invoice Number")]
     public virtual string UsrLinksoftARInvoiceNumber { get; set; }
     public abstract class usrLinksoftARInvoiceNumber :         PX.Data.BQL.BqlString.Field<usrLinksoftARInvoiceNumber> { }
     #endregion
 }

This field stores an external invoice number (e.g., from a third-party system like Linksoft). It’s saved directly in the ARRegister(ARInvoice) table and visible on invoices.

public class ARAdjustExt : PXCacheExtension<PX.Objects.AR.ARAdjust>
{
    #region Activation
    public static bool IsActive()
    {
        return DialTow.Activation.IsActive();
    }

    #endregion

    #region UsrLinksoftARInvoiceNumber
    [PXDBString(50)]
    [PXUIField(DisplayName = "Linksoft AR Invoice Number")]
    public virtual string UsrLinksoftARInvoiceNumber { get; set; }
    public abstract class usrLinksoftARInvoiceNumber : PX.Data.BQL.BqlString.Field<usrLinksoftARInvoiceNumber> { }
    #endregion
}

This field appears in the document to apply tab of the ARPayment screen. The user manually enter inksoft invoice number here.
 

When the user enters a value in ARAdjustExt.usrLinksoftARInvoiceNumber, I want to:

1. Look up a matching ARRegister record where UsrLinksoftARInvoiceNumber = entered ARAdjustExt.usrLinksoftARInvoiceNumber value.

2. If found, populate the ARAdjustExt.refNbr with the refNbr from that invoice.

protected void _(Events.FieldUpdated<ARAdjust, ARAdjustExt.usrLinksoftARInvoiceNumber> e)
{
    ARAdjust row = e.Row;
    var ext = e.Cache.GetExtension<ARAdjustExt>(row);

    if (ext?.UsrLinksoftARInvoiceNumber == null)
        return;

    // Querying ARRegister for matching UsrLinksoftARInvoiceNumber
    ARRegister arRegister = PXSelect<ARRegister,
        Where<ARRegisterExt.usrLinksoftARInvoiceNumber, Equal<Required<ARRegisterExt.usrLinksoftARInvoiceNumber>>>>
        .Select(Base, ext.UsrLinksoftARInvoiceNumber);

    if (arRegister != null)
    {
        e.Cache.SetValueExt<ARAdjust.adjdRefNbr>(row, arRegister.RefNbr);
    }
}
I use this updater on ARPaymentEntry extension.but it not fetch vaues as expected.
(

public class ARPaymentEntry_Extension : PXGraphExtension<PX.Objects.AR.ARPaymentEntry>
{
    public static bool IsActive()
    {
        return true;
    }

    #region Event Handlers

    protected void ARAdjust_UsrLinksoftARInvoiceNumber_FieldUpdated(PXCache sender, PXFieldUpdatedEventArgs e)
    {
        var row = e.Row as ARAdjust;
        if (row == null) return;

        var ext = PXCache<ARAdjust>.GetExtension<ARAdjustExt>(row);
        if (string.IsNullOrEmpty(ext?.UsrLinksoftARInvoiceNumber)) return;

        // Find matching invoice by Linksoft AR Invoice Number
        var invoice = PXSelectJoin<ARInvoice,
            InnerJoin<ARRegister,
                On<ARInvoice.docType, Equal<ARRegister.docType>,
                   And<ARInvoice.refNbr, Equal<ARRegister.refNbr>>>>,
            Where<ARRegisterExt.usrLinksoftARInvoiceNumber, Equal<Required<ARRegisterExt.usrLinksoftARInvoiceNumber>>>>
            .Select(Base, ext.UsrLinksoftARInvoiceNumber)
            .FirstTableItems
            .FirstOrDefault();

        if (invoice != null)
        {
            row.AdjdRefNbr = invoice.RefNbr;
            row.AdjdDocType = invoice.DocType;

            sender.Update(row);
        }
    }

    #endregion
also try this field updater, but not working)

I would really appreciate any advice, sample code, or direction on how to properly fetch a value from ARRegister using a custom field added through a DAC extension.

Thank you.