SHiFT Code Failed

I entered in a SHiFT code that hasn’t expired yet and it said the code I have entered cannot be redeemed. I entered it again to see if I misspelled it but the same thing. I tried putting another code just in case the one I put had expired but same thing. I then hard resetting my PS4 and repeated the process but still the same process. I don’t know if I missed something or am doing something wrong. Any help would be much appreciated, thanks.