Hello Zhi_Hong,
Just checked your ticket information and you were good to go 
Could you please inform your invite code and ticket related to this issue, so I could have a further look?
Also, a note to everyone here:
If you fail the payment verification, any subsequent purchases will always be placed Under Review until a Gameflip representative reaches out to you. Please note that you will only have a few hours to input the code before being canceled.
Next time, if you are unable to find the 4 letter code, send us a screenshot of the description line for this purchase in your credit/debit card’s online statement so we can try to find it. Feel free to block out any unrelated information to protect your privacy.
God speed!
