Following their recent announcement regarding them having to suspend the Content Information Screen and What’s New? services for the Playstation 4, Sony Computer Entertainment Europe have confirmed that the “Redeem Voucher” functionality has also been temporarily disabled.
This is what Fred Dutton, SCEE Blog Manager had to say on this announcement:
We are aware that users are experiencing some disruption to the PSN service. To minimise the inconvenience we have suspended the “redeem voucher” functionality whilst we investigate further. Unfortunately this means that money cards, product vouchers, PlayStation Plus vouchers, PS3-PS4 upgrade vouchers and any other vouchers for digital content are not redeemable at this stage. Other PSN features such as log-in, online multi-player gaming, PlayStation Plus trial, PS Store (excluding voucher redemption), trophies, messages, friends etc. are all available.
You can redeam PSN+ voutchers on a PS3 right now, you can also redeam prepaid cards on the web account managment.