Not received checkout callback after payment is complete in sandbox mode about nextgen-android HOT 3 CLOSED

       try {
            CFPaymentService.getInstance().setCheckoutCallback(this)
        } catch (e: CFException) {
            e.printStackTrace()
        }
 

private fun startPayment(token: PaymentToken) {
        if (token.cftoken.isNullOrEmpty() || token.order_id.isNullOrEmpty()) {
            toast("Something went wrong. Please try again later")
            return
        }

        try {
            val cfEnvironment =
                if (SERVER_MODE == "1") CFSession.Environment.SANDBOX else CFSession.Environment.PRODUCTION

            val cfSession =
                CFSession.CFSessionBuilder().setEnvironment(cfEnvironment)
                    .setOrderId(token.order_id)
                    .setOrderToken(token.cftoken).build()
            val cfTheme = CFTheme.CFThemeBuilder().setNavigationBarBackgroundColor("#fc2678")
                .setNavigationBarTextColor("#ffffff")
                .setButtonBackgroundColor("#fc2678")
                .setButtonTextColor("#ffffff")
                .setPrimaryTextColor("#000000")
                .setSecondaryTextColor("#000000")
                .build()
            val cfPaymentMethods = CFPaymentComponent.CFPaymentComponentBuilder()
                .add(CFPaymentComponent.CFPaymentModes.CARD)
                .add(CFPaymentComponent.CFPaymentModes.UPI)
                .build()
            val cfDropPayment =
                CFDropCheckoutPayment.CFDropCheckoutPaymentBuilder()
                    .setSession(cfSession)
                    .setCFUIPaymentModes(cfPaymentMethods)
                    .setCFNativeCheckoutUITheme(cfTheme)
                    .build()
            val gatewayService = CFPaymentGatewayService.getInstance()
            gatewayService.doPayment(this@PaymentActivity, cfDropPayment)
        } catch (e: CFException) {
            e.printStackTrace()
        }
    }