Sony has reportedly disabled PlayStation Plus pre-paid code redemption for existing subscribers ahead of the transition to the new tiered version of PlayStation Plus in June.
As reported by Eurogamer and PushSquare, some users are unable to redeem their prepaid PS Plus and PS Now subscription cards, presumably to stop users from locking in the new tiers of PS Plus at a cheaper price. In the FAQ for the new PS Plus, PlayStation states that users who are subscribed to both PS Plus and PS Now will be switched over to the highest tier, PS Plus Premium, when the transition is made. The length of the subscription will be based on whichever subscription is longer. Since the service was announced, users have begun stacking their subscriptions in anticipation of them being converted to the new service.