Protip - You can claim the free game at GOG.com by visiting https://www.gog.com/giveaway/claim

https://www.gog.com/giveaway/claim

It will give a json response. Visiting a second time should return "Already claimed" if it worked.

This helped me to get around an issue I had with the link not loading on the main gog.com page when there was a free giveaway. (Credit)

(If you still have trouble, make sure you are logged in before clicking)