Update a custom checkbox value(PO Screen) in a rowUpdated event handler from PORecieptEntry graph

In Acumatica, I want to update UsrSendPONotifications checkbox(which is in PO screen) to true when I update a row in corresponding PO Receipt. This is the code that I tried & it is not working. So , UsrSendPONotifications checkbox remains false. Any idea about this?

protected void POReceipt_RowUpdated(PXCache cache, PXRowUpdatedEventArgs e)
{
      
    var row = (POReceipt)e.Row;
    if (row == null) return;
    else
    {
        POReceiptLine receiptLine = new PXSelect<POReceiptLine, Where<POReceiptLine.receiptNbr, 
        Equal<Required<POReceiptLine.receiptNbr>>>>(Base).Select(row.ReceiptNbr);
        if(receiptLine == null) return;  
        else
        {
            POOrder poOrder = new PXSelect<POOrder, Where<POOrder.orderType, 
            Equal<Required<POOrder.orderType>>, And<POOrder.orderNbr, 
            Equal<Required<POOrder.orderNbr>>>>>(Base).Select(receiptLine.POType, 
            receiptLine.PONbr);

            if(poOrder == null) return;
            else
            {
                POOrderExt poExt = poOrder.GetExtension<POOrderExt>();
                poExt.UsrSendPONotifications = true;
                cache.SetValueExt<POOrderExt.usrSendPONotifications> 
                (poOrder,poExt.UsrSendPONotifications);
                    
             }
       }
 }