Sony has seemingly disabled the ability to redeem PlayStation Plus codes from third-party retailers, or via the PlayStation Store.

Some users have tried to extend or 'stack' their PlayStation Plus membership after news broke that those with simultaneous PS Plus and PS Now subscriptions will get upgraded to PS Plus Premium in June, with the length of the new subscription being equal to their longest current memberships.

But, after purchasing a PS Plus code, users then reported the codes being rejected after an attempted redemption.

This is now a widespread issue, with some evidence that Sony support will also not accept the codes. Examples of this can also be found on ResetEra forums, with one user being told: "On this case right now you will be unable to add those codes to the account since we have disabled the option to redeem PS Plus codes." IGN was also contacted by a user who reported the exact same line being given to them by support.

Stacking a membership is where a user can use pre-paid cards to redeem an extension to their current membership. For example, a user with 12-months left of PlayStation Plus could previously buy another 12-months, stacking their membership to 2-years, even before the subscription expires. This is typically common practice when PlayStation Plus codes are discounted during sale events.

It is now believed by some in the PlayStation community that Sony has blocked this to prevent users from further taking advantage of making any savings on the revamped PlayStation Plus service. Sony has offered no official word, so IGN has reached out for comment.

Many users had already stacked PS Now memberships, after it was announced those with a PS Now account would be upgraded to PS Plus Premium at no extra cost. This loophole was also quickly shut down, and PS Now memberships are no longer available to purchase.

Robert Anderson is a deals expert and Commerce Editor for IGN. You can follow him @robertliam21 on Twitter.