Apple TV Showtime App Access Issue

I purchased showtime through Apple TV, the subscription purchase is showing in my purchases; but I cannot access showtime through the showtime app loaded on my apple tv app page. When I try to access the app to watch showtime it wants me to set up a new account, start a 1 month free subscription; if I try to use the email address associated with my apple account it says no account exists with this email address? Can someone tell me how to access my showtime subscription through my apple tv showtime app please?