if you're still having problems the solution is easy
first - what system are you on, windows or macosx?
either way - make absolutely sure the fun_plug file has NO extension - on macosx it auto-adds .sh as an extension if you are unsure either way - simply open the file in a plain text editor and copy its contents into a plain file and save it as fun_plug - with no extension, also remove any whitespace at the bottom!
i'd also recommend placing a copy of fun_plug and the fun_plug.tgz files in BOTH your volumes - because it depends on which drive is your *real* volume_1 (the dns-321 names whichever drive - regardless of left or right, volume_1 as the first drive inserted)
finally - reboot, and wait about 5 minutes - as the dns-321 is slow to deflate the .tgz
check both volumes for an ffp folder and ffp.log
please post your results
p.s. sorry if this was answered already as i didn't want to read through 5 pages of forum on here
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good luck!