Strong is missing from my Apple Watch
If you've recently updated Strong using the App Store and the app has disappeared from your Apple Watch, this may have happened because you're using an older version of watchOS.
In order to use Strong to your Apple Watch, you'll need to update to watchOS 4.0 or later. This requires iOS 11, which is available on iPhone 5s or later.
To install Strong for Apple Watch again, open the Watch app on your iPhone, and in the My Watch tab, tap Install next to Strong. After installing Strong, you may need to re-sync your iPhone and Apple Watch by going to Settings > Apple Watch in Strong and tapping Reset Strong for Apple Watch.