It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

is there any reason why this game doesn't t have a discount in the sale?
While there are a few newer games that are part of this sale, most of the games released in the last two or three months are not discounted. Since this game only came to GOG at the end of August, it's probably just too new to be included in a sale like this. Sorry, but maybe you'll have better luck during the Winter Sale next month?