Is it the same field in both cases? If the second example is for a different field, check to see if it is defined as a text or number field. If it's a number field, this may not work.
The next possibility is that datafield contains "GN04", but there is additional, possibly invisible text in the field. If so, a find will find the record but if you click into the field and try to highlight the contents, you may find that there is also a space or return character in the field.
Thank you for helping me find the invisible spaces.