FulVal: Please stick that post, or this will happen again, again and again...
It will happen again, again and again. Because GOG Connect is still promoted on every GOG page, because its page still claims it works, and even though it doesn't work at all you can still hook up a steam account with it - I checked with a newly created one some time ago.
SmollestLight: As ConsulCaesar has already pointed out, the GOG Connect offers were time-limited and are no longer supported.
Might be a good idea to decouple account link-ups and remove the page and the link to it from the bottom bar for the time being, because otherwise newcomers will keep taking the pitfall and asking support or posting on forum about this.
Although, in hindsight, I think the whole idea wasn't good from the business perspective to begin with. If people buy on Steam (and since many games are cheaper there there's some incentive to for those that don't feel strong about DRM-free gaming), and get a free GOG copy, GOG's profits take a hit, and worse, unlike people who don't have those games on GOG there's no chance they would buy them sometime down the line. I like occasional 90% off offers much more, in any case.