At times, you can enter the correct Walmart code and it will give the "The gift card number and PIN you entered do not match. Please try again." error.
This is most likely due to your gift card code been locked probably because it has been accessed using a bad IP.
When checking your Walmart gift card balance, do not use any IP other than the USA and do not use VPN, it can lead to such error, but not in all cases.
Unfortunately, Cardtonic cannot rectify this error.
Head back to the store where the gift card was purchased to get it rectified.
To check your Walmart gift card balance, click here