Welcome to Apple Support Communities.
I understand your issue is Safari won't play videos.
If video playback is not working, you should clear Safari history and website data. Go to Settings and choose Safari. Tap Clear History and Website Data and when a pop-up window shows up, confirm your action by tapping on Clear History and Data.
Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch
You can also try force quitting Safari and launch it again.
- Tap on the Home button twice
- You will see a preview of the apps you have been using
- Swipe left or right to find the app
- Once the app is closed, go back to the Home screen and open the application again.
You need to make sure the apps on your device are up to date. Every update always comes with some improvements, new features, and bug fixes. That’s why, if your iPhone video playback is not working on the certain app, update it to the latest version.
- Launch the App Store
- Tap the Updates section in the bottom-right corner
- You can select Update All or find a certain app and tap the box next to the app name to update it.
Also, make sure your iPhone is up to date to the latest version of iOS, which is 11.0.2.
- Make sure your iPhone is charged or connect it to a power source
- Connect to a Wi-Fi network
- Navigate to Settings > General > Software Update
- Tap Download and Install or Install Now
Enjoy your day!