Able to show the promotional offer, but after going through the payment process, inputting my password, and confirming the purchase, I get an error popup that says "Unable to Purchase. Contact the developer for more information." In the logs, I get the following errors: SKErrorDomain Code=12 "(null)" ASDServerErrorDomain Code=3903 "Unable to Purchase" Here are the example parameter values I am passing to the combined string appBundleId + '\u2063' + keyIdentifier + '\u2063' + productIdentifier + '\u2063' + offerIdentifier + '\u2063' + appAccountToken + '\u2063' + nonce + '\u2063' + timestamp appBundleId: com.app.myapp keyIdentifier: copied the key ID from the App Store Connect productIdentifier: product_identifier offerIdentifier: offer_identifier appAccountToken: tried both a UUID and an empty string nonce: a UUID to lowercase timestamp: UNIX timestamp How I'm generating the signature (Java) /* promotionalOfferKey = value between "-----BEGIN PRIVATE KEY-----" and "-----END PRIVATE KEY-----" from the downloaded p8 file from App Store Connect associated with the keyIdentifier parameter above */ // stringToSign = the combined string above byte[] encoded = Base64.getDecoder().decode(promotionalOfferKey); KeyFactory keyFactory = KeyFactory.getInstance("EC"); PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded); Signature ecdsaSign = Signature.getInstance("SHA256withECDSA"); ecdsaSign.initSign(keyFactory.generatePrivate(keySpec)); ecdsaSign.update(stringToSign.getBytes(StandardCharsets.UTF_8)); byte[] signature = ecdsaSign.sign(); signatureToReturn = Base64.getEncoder().encodeToString(signature); What am I doing wrong? Thank you in advance.