Well, I had the EXACT SAME PROBLEM. I had a brand-new, factory-sealed game, and I had just scratched off the coating to reveal the code be fore putting it in. The code was rejected both from the PS Store, and from the Account Management menu of the PS3 (which is where the voucher tells you to input the code.)
So, I actually called up the Sony Support number that's listed on the Voucher itself, explained the problem, and the phone tech said for me to email a copy of the front/back of the voucher and my receipt as proof of purchase. I emailed the required contents and received an automated message saying they would respond in 3-5 days with a solution.
After a whopping 13 days, I FINALLY got a response from Sony. Here is the response from the support tech:
Dear (my name),
As it is clearly stated on the voucher you sent in to us, this code will become active on April 12, 2013 - NO EARLIER THAN THAT DATE.
Please be patient, hang onto your code and redeem it **ON OR AFTER APRIL 12, 2013**.
The text on the voucher states this verbatim: [Valid* Game Launch - 4/12/2013]
Are the Sony Support Tech's REALLY this stupid??? How could you possibly interpret that to mean that the valid code time BEGINS on 4/12/2013 (and even if it did, then when does it expire, GENIUS?)?
What the voucher is ACTUALLY saying is that the game code is valid from the date the game launched up until 4/12/2013.
(in plain english)
Code Valid Start Date: Game Launch Date
Code Expiration Date: 4/12/2013
Why in the name of all that is good an holy would a game developer only make a code valid A FULL YEAR after a game's release and then have no expiration date whatsoever? The game was launched on May 3rd, 2011. Are you honestly going to sit there and tell me that Evolution Studios (the developers of this game), put voucher codes in this game box back in April of last year, and expected the people who bought the game on Launch Day to play for an ENTIRE YEAR before being able to redeem the code contained in the box?