Hello James,
It sounds as though your Apple Watch is successfully mapping your workout, but it's not appearing in the Fitness app on your companion iPhone. If you're only having this issue, and not having the following issues we recommend reaching out to an available Apple Support channel through the Get Support website.
If you're experiencing issues with the Activity application, Heart Rate app, or other health-related apps failing to launch or load data on the Apple Watch, Health app doesn't launch on companion iPhone, Health is using a large percentage of storage in Settings > General > iPhone Storage, or you see the Activity using a large percentage of storage in Settings > General > Usage on your Apple Watch, or you see an increase in battery usage for the Health app on the companion iPhone shown in Settings > Battery please let us know if you updated to iOS 14 and watchOS 7 from iOS 13 and iOS 6, or if you updated directly to iOS 14.0.1 and watchOS 7.0.1.
If you're running iOS 14.0.1 and watchOS 7.0.1 let's continue by unpairing the Apple Watch using the following steps.
- Open the Watch application on the iPhone.
- Tap the My Watch tab, followed by All Watches
- Next to your watch tap the "i", followed by Unpair.
This will automatically back up your Apple Watch. Once unpaired please go in to Settings [your name] > iCloud and confirm Health is enabled to sync to iCloud. Once enabled, or if already enabled return to Settings > [your name] > iCloud > iCloud backup, then tap backup now. Once the backup completes confirm that it shows as being completed. You can also use the following article to verify the backup has been completed.
Locate backups of your iPhone, iPad, and iPod touch
Once backed up please go in to Settings > General > Reset > and tap Erase all Content and Settings. After the erase completes, set up your iPhone, and restore to the backup. Once the iPhone has been restored to the backup pair your Apple Watch, and restore to the Apple Watch backup.
If you continue to have issues after those steps please refer to the Get Support website, and reach out to an available support channel.
Have a great week!