Successful transaction doesn't trigger "When an order is first paid in full" rule

Firstly thanks for this great module.
Reg. the issue, as mentioned in the title, upon checking out successfully using PayUmoney gateway, the event "When an order is first paid in full" is not triggered. This is the standard event that a payment gateway should trigger upon a successful transaction.

EDIT: It seems that the "payment" tab in the order page "admin/commerce/orders/xx/payment" is empty even after the transaction. I guess the payment and the order is not referenced properly and that is the reason behind it. I will see if I can find the cause.