Thanks everyone.
I did indeed think Kovid was talking about deleting the access key.

This is because there
is no ISBN number in the metadata box, just the isbndb access key in the access key box. I am only searching via author and title; I haven't input an ISBN number.
Back to my original question - if there is no ISBN number in the metadata box, then the program searches both the ISBN database and Google Books, is that correct?
I will do as Starson17 suggested and simplify the search terms - I thought you had to put the full title and the complete author's name so that was what I was doing.
I keep telling myself this isn't rocket science. Wait until I try to use Calibre to actually convert a eBook to a different format!
Holly