Probably because that offer was available 7 1/2 months ago. So the link is probably broken by now.

Also, when we do get the freebies, they're sometimes given only to selected members. No one (to my knowledge) has worked out the selection process, it just seems to be a randomly generated thing.

However, sometimes, the links do work for those that didn't receive the offer, but in this case, even if the above link did still work, that particular promotion ended over 7 months ago.