Where did you get this voucher? What makes you so sure that it has not expired? You have to contact Playstation customer support by phone or live chat (https://support.us.playstation.com/app/contact_opt
is says i put it in wrong or it expired both are false
First all. If this is prepaid PSN card then make sure that it was activated. This should be reflected on the receipt.
With that said, speaking from my own experience, some letters in these vouchers can easily be mistaken by numbers. For example, the time in which I've ran into this issue is because I was confusing the letter G for the number 6. Double check the characters.