Seems some people are having trouble accessing the PlayStation Network right now, being either unable to sign in or finding their ability to stay connected being "disrupted". So Sony is trying to lighten the network's load.
The company has disabled the "redeem voucher" function on the PSN while they "investigate further". Given the timing of the network troubles and the first thing Sony disabled, it doesn't take Sherlock Holmes to deduct the problem might just be that a ton of new games, codes and consoles got sold on Black Friday, and a lot of Americans have the day off (though reports of spotty service are worldwide, so the new PS4 consoles sold in Europe probably aren't helping).