Account to view refund on Mastercard Debit card is failing

I received a letter saying I got a refund from XFinity loaded on a Mastercard debit card. I went to xfinityrefunds.com, and entered the card number and created an account with my email (a gmail email). It then demanded a verification code that was sent to my email, but a comcast.net email instead of gmail. I have never opened a comcast email. So I set up a comcast email at the address it wanted to send my verification code to, and resent the code several times. I never received the verification code to either my comcast email or my gmail. I am wholly unable to view any information about my card. There is no option to change the verification method or email that it is being sent to. 

(I also attempted to add my card to Apple pay, as the letter said it could be used in mobile wallets. It let me add the card details, then demanded a verification code sent to some number ending in 4330. That number means nothing to me---it is not any of my phone numbers or anything.)