2. Restart iPhone
Hold the Power button for seconds until the “Slide to power off” appears, turn off your iPhone. Then press the Power button to turn on your device, open Health app to check if the data appear or not.
3. Update Software
Go to Settings -> General -> Software Update, tab “Install Now” and then follow the automatic instructions to download and install the update. When the process completes, your lost information in Health app will be recovered successfully.
4. Force Reboot iPhone
If the iPhone health app still not showing any data after trying the methods above, you may need to force reboot your device. Hold and press the Home button and Power button until you see the display go blank and the Apple logo appears.
5. Restore Health Data from iCloud/iTunes Backup
If you have backed up your device in iCloud or iTunes, you can restore health data from the backup easily.
Go to Settings > General > Reset. Then tap Erase All Content and Settings
Turn on device and follow the setup steps until you reach the Apps & Data screen, then tap Restore from iCloud Backup
Sign in to iCloud and choose a backup to start transferring. Depending on the size of the backup and the network speed, the progress bar might need a few minutes to an hour to complete.