regarding dying light additional content
"...you won't be able to access that content without internet connection" - verified by me
"apparently it unlocks based on the clock that synchronises with the internet connection, so while it is in the files, it's inaccessible without at least a brief connection."
"You are the first user to ever write to us about it and I suspect it's because you do need internet connection to download anyway, so it affects only a very small group of our users." - logical. i mean who would disabled their internet just to test something so small. me.
"But it's still something I'm unable to fix for you" - maybe it's handled by techland. they perhaps chose an internet based solution. and anyway, there are more "exclusive dockets" which we are missing because techland wants to take advantage of account linking. you can check the dying light sub-forum here on gog.
they also offered me a refund. very polite of them but unnecessary in this case. i don't think gog can do much in this case but i don't think/hope gog is at fault here, although i can't help thinking things may have played out differently if galaxy didn't exist.