how to identify why lookup failed in SSIS

i have created an ETL package and having a lookup to match userid in db. i checked in dataviewer what data is going as input to my lookup. the data is correct and the table i used in lookup to match also having data for that input but still i am getting error that no matching records found. > **example for my schemario:** i have a view that fetches data like > orderby, orderno, orderdate. **orderby is a usercuid nchar(64)**. i have a > Dim in Dw named DimUser which is having usercuid. and i have to get > DimUserId for matching usercuid. in my input data i am getting > **orderby as "User1"** and in my DimUser there is record with > **usercuid=User1** but **still ETL is failing with no matching records**... anybody could suggest how could i find out what is the problem?