[dba-SQLServer] join pulls no records

I have two tables.  Each has an nvarchar 50 field which contains a string
consisting of the first 5 characters of about 5 different fields, which is
called in the client's industry a "match code" and is used to find the same
name / address record in a different table.  I have made the field the PK,
so there is an index and it is unique.  A join of the two tables pulls no
records.  I can manually look in the two tables and see visually identical
data, i.e. it looks like the match code matches but an inner join does not
pull records.
 
Any clue why not?
 
John W. Colby
Colby Consulting
www.ColbyConsulting.com