Buzzb, I believe Murky’s view, though he may correct me, is that cells connected diagonally would be contiguous (see his post #64). Thus he sees that occurrence as a possible solution, ruled out only by the mathematical constraint of adding to 39 (or 40).
I consider contiguous to mean connected by a side, rather than a corner, so I wouldn’t consider it a possibility. Either way, it’s a shame it could not have been specified in the preamble.
You might wish to ask admin to remove the first word of your post