PayPal Integration throwing error

Anybody experienced in C# .NET and worked in PayPal integration before? I have been trying to integrate my .NET website with PayPal using REST API. Once the payment is authorized by the customer; the rest API is re-directing me to the URL for the successful transaction. I fetch the details like Payment ID, token, payer ID etc. information. Everything goes smooth till this point. When I call the execute payment; it throws back the 401 not authorized error. public Payment ExecutePayment(string paymentID, string token, string PayerID) { APIContext apiContext = new APIContext(token) { Config = [login to view URL]() }; PaymentExecution paymentExecution = new PaymentExecution() { payer_id = PayerID }; Payment payment = new Payment() { id = paymentID }; Payment executedPayment = [login to view URL](apiContext, paymentExecution); return executedPayment; }