Problem when trying creating an Apple Pay payment token

Hello Dears, We're trying to setup apple pay button on our website with a payment gateway We're in the token step Creating an Apple Pay payment token is the first step to creating a Tap(Payment gateway token) when we're sending the certificate to the apple endpoint we should send it as a PEM file, not CER The error that we got

"message": "unable to set private key file: '/Users/a/Documents/Sites/ish/storage/apple-pay/tap-payment/apple-pay.pem' type PEM",

since we contact the payment gateway the advised us to contact apple support.. can you help us please.

Thanks for understanding

Problem when trying creating an Apple Pay payment token
 
 
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