Paypal — didn't receive the cashback for one of the transactions

I booked one flight from yatra.com and paid through paypal account and there was one offer for first time paypal users to get 500 cashback in paypal account. I booked the flight and was cancelled by yatra by some reasons and amount got refunded back and also the cashback was withdrawn from my paypal account as it was a cancelled transaction (Which i didnt cancelled). I booked the flight again and this time the transaction was successful and was supposed to get the cashback this time but didn't get.

I spoke to customer care of paypal and they are giving some weird reasons and now they are not responding as well.

Please look into the matter and do the needful.