Every time it says server problem or not authorized, anyone knows about this ?

Same here, looks like a Galaxy problem.

Im having the same problem using the Galaxy Client, i downloaded the update and the new dlc from the gog.com website.

Tried installing it, works like a charm. What you do probably is clicking on the DLC installer, that is not the way to install them though.

Click More>Configure>and tick the checkboxes next to the DLC you wish to install.

I clicked More, Manage and verify. Then tried to run the DLC install and the message next to the More button now says Server Problem.

I can only assume it's a GoG issue. I'll check again tomorrow.

Tried it again and it says 'server error' now, guess the servers are down. Guess everyone tries to download it at the same time or they realized the problems with the Wolf gear and fixed it quickly.

Same problem ;) Trying to DL something like 17Mo and Server problem. i guess we have to wait ^.^

Plz dear god, guys move yo ass and go to the website and download the update and dlcs manually. :D The download still works there! If you download it using the galaxy client or manually makes no difference.

Q.: Upon installing the retail copy and redeeming the code on the website, the game fails to update through Galaxy with the status set to NOT AUTHORIZED.
A.: You need to 'purchase' the free DLC program first, once that is installed it should automatically go on with the updating process.

FAQ: http://www.gog.com/forum/the_witcher_3_wild_hunt/faq/post1