Please make a distinction between a subscription as started in the separate Starz app and a subscription as started in Apple TV app Channels. These subscriptions are generally not exchangeable, even though both can be billed through iTunes, and both can feature their content in Watch Now and Up Next of the Apple TV app.
Please contact Starz about the availability of episodes of shows on Starz/Starzplay. The Starz app would get its content directly from the Starz servers. Apple TV app Channel Starzplay would get its content from the Apple servers, and that would meant that Apple has to receive the files first to make them available.
Episode 7 should be released 2020-06-28. Let them know if you experience a delay in availability. Keep trying to see if availability has changed.