MyPoints reward's just been Refunded. Somebody tell me why? Thanks!

i tried to redeem my points to AMZ giftcard 4 days ago. But now, my reward is refunded to my points balance. Somebody told me that maybe my account's not been verified. But i've not been received any verify requesting. Or may i have to complete my profile account info before redeem ? IF someone know my problem, pls help me. Thanks!