At the moment nobody can buy a year's worth of subscription. The reason AFAIK is that Shuffle iT only has the license until the end of 2019 (of course, it might get extended), so it cannot promise to do anything after 1/1/2020. I assume that is the reason the code doesn't work.
See my post below for a corrected reason.
Of course, the optimal solution would be to allow the code until end of the year and then extend it once the license got extended or transfer the dates to the next license holder (if another party gets it).