Made an account to literally comment on this thread. They absolutely know wtf they are doing. I purchased a code to extend my ps plus since it ends next month and I am unable to redeem it. I also cannot extend on the UI. My wife, who is NOT a ps plus member, was able to purchase it without any issues whatsoever. I contacted support and this is how the convo went:
Alexandra M.: Thank you for the details! What I have checked is that we have being notified there are some incidents trying to redeem it and actually, our special team is already working to get it fixed
She then proceeded to ask if I did PC or console to redeem. I explained I did both. She had me copy/paste my code to her to confirm it is valid. She told me it was valid and she will check into it a bit further. She then said this contradictory statement:
Alexandra M: Thank you so much for waiting! Due to the upcoming changes in the PS plus subscription, currently the PS Plus stacking is not available as we have removed the ability to do that. We understand how important this is for you and we will have answers on how this will work once the new PS plus membership becomes available. Please visit our blog https://blog.playstation.com/ for more details to come on these changes to our services.
I asked politely, "So, you guys blindly disabled a feature without letting anyone know? I wonder what you would do if your electricity got cut off without notice and your bill was current..hmm" She followed up with this stupid statement:
Alexandra M: I understand how frustrating this must be. I can only advise you wait until your current subscription is over then use your code. Extension/stacking is no longer available. Do you have any other concerns?
Nope. Bye.
So yea, sony can piss off.