Here are several reasons that cause the transactions failed.
Wrong transfer amount.
Different sender name (the payment didn’t match with the sender's bank account).
Wrong recipient details (this includes incorrect bank, name didn't match with the registered name on banks, incorrect address, incorrect phone number, wrong bank branch code, etc).
Transaction expired after payment has been made (the transaction is expired due to the sender forget to press "I Have Paid" button).
Payment rejected by our Compliance team.
If your transaction failed, sure you can request for a refund. See how to make refund request here.