Cashwalk added a new feature where you have to verify every time you redeem a gift card.
But phones have a feature that blocks or silences all numbers that are not in your contacts.
So this is what you do:
When you press the button to verify you will get a call that is silenced then the call goes straight to voicemail.
Go get the number and add the number in your contacts as Cashwalk or something.
Then go to verify again.
You will now get the phone call where you are able to answer.
Make sure you memorized the 6 digit number it gave you before the verification call.
Type in the number then press #.
You will now be verified for that gift card. Just remember you have to do this every time you redeem a gift card.
If it still doesn't work it is possible that you blocked the number at some point so go to your blocked numbers list and unblock the following number 201-350-5791.
Hope this helped.