If the Reader was added and new columns were added after the Reader was added you might want to try ReAdding the reader.

What might be happening (and is a fairly common problem) is that when you first add a Reader FME will scan the data and create a schema based on that data/those columns. If you then add new columns but don't Re-add the reader (or update the feature type) then FME doesn't know about the new columns.

Another possible issue is that you have defined the Reader based on a 'Named Range' where the Named Range contains some, but not all, of the columns. Check that if reading a Named Range that the columns which are missing are contained in that range.