Process PayPal payments lead to Payer has not approved payment error - paypal

Question

I have implemented PayPal payment described here
https://developer.paypal.com/docs/api/quickstart/payments/ with provided Java SDK which use API /v1/payments
<dependency>
<groupId>com.paypal.sdk</groupId>
<artifactId>rest-api-sdk</artifactId>
<version>1.14.0</version>
</dependency>
Step1 : Create payment as describe in above link and it will create payment at PayPal and we got approval_url which is shared to customer to complete payment.
Step2 : There is a webhook listener for only one event there
Step3 : when my application receives that event from PayPal then it executes payment as described in above link
This is working for most of the payment case, but few payments, during payment execution following error get occurred.
{"name":"PAYMENT_NOT_APPROVED_FOR_EXECUTION","message":"Payer has not approved payment","information_link":"https://developer.paypal.com/docs/api/payments/#errors","debug_id":"8c19669326adc"}
Now, this is not clean what is different between payment which lead to successful execution and other which lead to failure with "Payer has not approved payment" message. And what should be done to solve issue here?

Answer 1

When an old deprecated API v1/payment (or with the current API, a v2/checkout/order) is created, it is in an unapproved state. For it to be executable (or with v2, capturable) a payer must log into a checkout and approve it.
If no one logs in and approves a payment, it remains in an unapproved state.
When you attempt to 'execute' a payment (or with the current v2/checkout/orders API, 'capture' an order) that has not been approved by a payer, you will receive an error message stating that the payment has not been approved.
You can only execute payments (or capture orders) that have been approved.
For best results, use the current v2/checkout API with an in-context approval flow. Make two routes on your server, one for 'Create Order' and one for 'Capture Order', documented here. These routes should return only JSON data (no HTML or text). When a capture response is successful, store its resulting payment details in your database (particularly purchase_units[0].payments.captures[0].id, the PayPal transaction ID) and perform any necessary business logic (such as sending confirmation emails or reserving product) before sending your return JSON.
Pair those two routes with the following approval flow: https://developer.paypal.com/demo/checkout/#/pattern/server