Hi Kawanhee4,
It sounds like you're having an issue playing a specific episode on your iPhone. If so, check out the steps below found from the article here: If you can't watch or stream movies and TV shows in the Apple TV app - Apple Support
"If the movie or TV show won't start playing
After each step, try to stream or download the movie or TV show again.
- Check the System Status page for service interruptions or check a third-party provider's website for any interruptions. If there are service interruptions, try to stream or watch the video later.
- If you're having trouble signing in with your Apple ID, you can reset your Apple ID password or learn how to get a verification code and sign in with two-factor authentication.
- If your cellular connection is poor, connect to Wi-Fi instead.*
- Try watching on a different device using the same Wi-Fi or cellular connection. If it doesn't work, contact your internet service provider to see if there's an issue with your network.
- If other people are using Apple TV+ or Apple TV channels, make sure it doesn't exceed the limits for streaming on multiple devices.
* Make sure that your Wi-Fi router is 802.11a/g/n/ac compatible. Streaming HD content requires 8 Mbit/s or faster. Slower tiers of Wi-Fi connections might not be fast enough to stream HD video content."
You can also test closing the app and a normal restart of your iPhone: Restart your iPhone
If you continue to have issue playing the specific episode after completing the steps, reach out to Apple Support directly to further assist. Get Support
Cheers.