After successful payment in paypal status remain goes to pending

Hi

I am using PayPal as a payment method, when i make an order and transfer funds successfully then my order status remains in pending not in process.

I have made payment through sandbox and standard account as well. And this issue i am facing is only one site. and i have try on other site and it work fine, don’t now why this site have issue, here is the link of the site

https://www.mantoproduce.com.au