Confirm Pokémon GO is connected with Google Fit or Apple Health.
Google Fit: Open Settings > Google > Google Fit > Connected apps and devices, and confirm Pokémon GO is listed as a connected device.
Apple Health: Open Apple Health > Sources, and confirm Pokémon GO is listed as a connected device.
For more information about Adventure Sync, please visit the Niantic support page at https://niantic.helpshift.com/a/pokemon-go/?p=web.
Note: The link takes you to a website that is not created or maintained by The Pokémon Company International.