Error in the server, I can´t install it. But i can install otthers games of my librery
I guess you tried to download it from Galaxy ? Can you try on the GOG website ?
Also, maybe you should remove your Galaxy database, I had a problem with a game that was non validated by Galaxy, the support team ask me to remove this file:
Probably you'll have to tell Galaxy where are located the other previously installed game.
Also, it's probably a problem on their server and you can't do anything about it. Try later.
If it doesn't works, you should open a ticket.