I have a MasterCard and every time I try to transfer my apple cash to my debit card it won't let me select it. it just asks me to add a card and then says it's already in my wallet and won't give me any other option to instant transfer it.
You cannot do an instant transfer to a Mastercard. Only to a VISA debit card. See: Transfer money in Apple Cash to your bank account or Visa debit card - Apple Support
You cannot do an instant transfer to a Mastercard. Only to a VISA debit card. See: Transfer money in Apple Cash to your bank account or Visa debit card - Apple Support
Instant transfer apple cash to mastercard
