need to fix a error in coinpayment gateway api

Job ID: 30916179

Budget: ₹1,500 – ₹12,500 INR

while i try to deposit btc in my ecommerce shop script it gives error , it uses coinpayment api so i checked the error log and it gave me this output : {
"error": "No 'buyer_email' set! If you cannot obtain the buyer's email and want to handle refunds on your own you can use your own email instead.",
"result": []
}

u can see the whole error which i uploaded as u can see in the pic ,
i dont know if the error is in my shop script or coinpayment itself ,if uu can surely fix this error i would love to pay