Filtering View Computed Column Returns Empty

Hi,

I created a Sales Order View with a computed column Payment Date. Payment Date is the latest CreatedDateTime of a payment made for a particular Sales Order. This field is displayed in a grid on form. The method is written as follows: 

public static server str latestPaymentDate()
    {
        DictView dv = new DictView(tableNum(SalesOrderHeaderView));

        str s = strFmt('SELECT TOP 1 CreatedDateTime1 FROM MCRCUSTPAYMTABLEVIEW WHERE MCRCUSTPAYMTABLEVIEW.RefRecId = %1 AND MCRCUSTPAYMTABLEVIEW.RefTableId = 2509 ORDER BY CreatedDateTime1 DESC',
        dv.computedColumnString(tableStr(SalesTable), fieldStr(SalesTable, RecId), FieldNameGenerationMode::WhereClause));

        return strFmt('ISNULL((%1), \'\')', s);
    }

I was able to sort the column but filtering it will return empty results every time and of course I have made sure the filtered value exists. I also tried advanced filtering statements like (Day(0)), (DayRange(0,0)) but still returns empty. 

What's more weird is, I have another computed date called Complete Date, which is the latest confirmation date for the sales order. No issue with this Complete Date field. 

So I thought there must be something wrong with my query. But I'm not sure what's wrong. The returned values are correct.

What else could be the root cause? 

Thank You.