why has my apple tv started asking me for a 3 digit code to rent movies when it never did before

I have apple tv and when I first set it up I had a gift card that I redeemed. I used that only to rent movies and it worked from my apple tv. I tried to set up family sharing and it just didn't work so I took it off and went back to the original Home sharing. Since then I had to add a credit card to my account. Now Apple asks me for the 3 digit code but it refuses to recognize it and repeats and repeats without any result. How do I fix this.