Hey there Jraculaa,
Do you recall if you subscribed to this app through the App Store/Apple or was it subscribed to online through the Starz website?
If done through Apple or the app on your device, make sure you see this subscription under Settings > [your name] > Subscriptions. If it's not appearing there, then it likely was subscribed to over the web through Starz directly. In that case, you'll need to reach out to their support team for help.
If you do see if the subscriptions through your settings but cannot access the paid content, use the steps here next: If you can't find or use your in-app purchases - Apple Support
Take care!