Incorrect function or parameter is incorrect.
Long story short:
DJOIN.EXE is finicky about its text formats. Don’t re-save a domain join blob text file with Notepad – if you can download the file as a file, you’ll be happier.
(Experimenting with Save formats in Notepad is left as an exercise for the reader)
I downloaded my domain join blob for DirectAccess offline domain join from a web server I hadn’t configured with a content-disposition of attachment, and Notepad opened the text file as soon as it was clicked – no Save option.
I then re-saved the file from Notepad. Mistake!
Notepad prepended an invisible byte order marker to the file. Which DJOIN.EXE didn’t like at all.
This BOM isn’t visible from Notepad, and FC didn’t find a problem until it was run with the /B switch (binary comparison) over a working and nonworking client.
I grabbed the file using another method, and it worked noicely!