How to resolve STPPaymentHandlerAction Status error Optional("No such setupintent: (null)")

i did all the code regarding to the Stripe and i followed the documentation of the stripe in which i i am calling one api to get the secret key from the server n which is coming..and after that i am passing it ot the "STPPaymentHandler.shared()"..but i am getting the error STPPaymentHandlerActionStatus error Optional("No such setupintent: (null)") a..please help me if you know thank you in advance below the code which i did

i followed this documentation https://stripe.com/docs/payments/accept-a-payment

//method to get secrete key

func checkout() {

    let apikey =  UserDefaults.standard.value(forKey: keyParameter.apikey.rawValue) as! String
    let dic = ["apikey":apikey,"amount":"5000"]
    Webhelper.sharedInstance.apiPostRequest(apiUrl: GlobalConstant.stripe_token, parameter: dic, success: { (success) in
        print("success from the server is \(success)")
        do{
            let responseResult = try Global.sharedInstance.decode(jwtToken: success)
            let message = Global.sharedInstance.getStringValue(responseResult["Message"] as AnyObject)
            if let status = responseResult["result"]  as? NSNumber {
                if status == 1{
                    let responseDic = responseResult["Secrate"] as! NSDictionary
                    self.setupIntentClientSecret = responseDic.value(forKey: "clientSecret") as! String
                    let apikey = responseDic.value(forKey: "publishableKey") as! String
                     Stripe.setDefaultPublishableKey(apikey)

                    print("  self.setupIntentClientSecret   self.setupIntentClientSecret \(self.setupIntentClientSecret)")
                }else if status == 0{
                    Global.sharedInstance.ShowMessagePopup(Viewobj: self, title: "", Message: message)
                }
            }

        }catch{
            print("cought error in the catch \(error.localizedDescription)")
        }


    }) { (error) in
        print("error for the server is \(error.localizedDescription)")
    }

}

///this is the method to complete the payment

@objc func pay() {

    // Collect card details
    let cardParams = self.paymentTextField.cardParams

    // Collect the customer's email to know which customer the PaymentMethod belongs to.
    let billingDetails = STPPaymentMethodBillingDetails()
    billingDetails.email =  "sunil@gmial.com"//emailTextField.text

    // Create SetupIntent confirm parameters with the above
    let paymentMethodParams = STPPaymentMethodParams(card: cardParams, billingDetails: billingDetails, metadata: nil)
    print("setupIntentClientSecret inside method\(setupIntentClientSecret)")
    let setupIntentParams = STPSetupIntentConfirmParams(clientSecret: setupIntentClientSecret)
    setupIntentParams.paymentMethodParams = paymentMethodParams
    print("secrete \(setupIntentClientSecret)")
    // Complete the setup
    let paymentHandler = STPPaymentHandler.shared()
     paymentHandler.confirmSetupIntent(withParams: setupIntentParams, authenticationContext: self) { status, setupIntent, error in
        print("success from the server is setupIntent\(setupIntent) status \(status) error \(error?.localizedDescription)")
        switch (status) {
        case .failed:
            self.displayAlert(title: "Setup failed", message: error?.localizedDescription ?? "")
           // print("\(error?.localizedDescription)")
            break
        case .canceled:
            self.displayAlert(title: "Setup canceled", message: error?.localizedDescription ?? "")
            break
        case .succeeded:
            self.displayAlert(title: "Setup succeeded", message: setupIntent?.description ?? "", restartDemo: true)
            break
        @unknown default:
            fatalError()
            break
        }
    }
}