I'm trying to add a promotional offer to my app. I've now managed to create a signature that my app gets back but when I try to make a purchase, I get an error saying "The operation couldn’t be completed. (SKErrorDomain error 12.)".
I read online it means there's something wrong with the signature. Can somebody guide me in the right direction to how I solve this?
Here's two pictures of what I've done so far https://imgur.com/a/5S2rQwC
Everything it feels like