I'm currently integrating Apple Pay with my payment provider, and I'm encountering a signature validation error during the payment flow. Here's the setup: I’ve verified that my Merchant Certificate is valid, and I'm able to initialize the Apple Pay session without any issues. Also this curl works fine The Payment Processing Certificate was created by my PSP. PSP claims that the payment token signature is invalid during the transaction phase, which prevents payment completion. The parsed signature starts like this 0:d=0 hl=2 l=inf cons: SEQUENCE 2:d=1 hl=2 l= 9 prim: OBJECT :pkcs7-signedData 13:d=1 hl=2 l=inf cons: cont [ 0 ] 15:d=2 hl=2 l=inf cons: SEQUENCE 17:d=3 hl=2 l= 1 prim: INTEGER :01 20:d=3 hl=2 l= 13 cons: SET 22:d=4 hl=2 l= 11 cons: SEQUENCE 24:d=5 hl=2 l= 9 prim: OBJECT :sha256 35:d=3 hl=2 l=inf cons: SEQUENCE 37:d=4 hl=2 l= 9 prim: OBJECT :pkcs7-data 48:d=4 hl=2 l= 0 prim: EOC 50:d=3 hl=2 l=inf cons: cont [ 0 ] 52:d=4 hl=4 l= 995 cons: SEQUENCE 56:d=5 hl=4 l= 904 cons: SEQUENCE 60:d=6 hl=2 l= 3 cons: cont [ 0 ] 62:d=7 hl=2 l= 1 prim: INTEGER :02 65:d=6 hl=2 l= 8 prim: INTEGER :16634C8B0E305717 75:d=6 hl=2 l= 10 cons: SEQUENCE 77:d=7 hl=2 l= 8 prim: OBJECT :ecdsa-with-SHA256 87:d=6 hl=2 l= 122 cons: SEQUENCE 89:d=7 hl=2 l= 46 cons: SET 91:d=8 hl=2 l= 44 cons: SEQUENCE 93:d=9 hl=2 l= 3 prim: OBJECT :commonName 98:d=9 hl=2 l= 37 prim: UTF8STRING :Apple Application Integration CA - G3 I'm looking for guidance on what could be causing this signature failure. Does anyone know what else I can check regarding the merchant or payment processing certificates, private keys, or key usage that might cause Apple Pay signature validation to fail, even if the session initializes successfully? Domains are also verified. Any help or suggestions would be greatly appreciated.