http://www.newsweek.com/pokemon-go-adventure-sync-how-1197748

Niantic revealed a new feature coming to its Augmented Reality games, including Pokémon Go ,called Adventure Sync. It’s now available for certain trainers.

Like other features, Adventure Sync in Pokémon Go is currently only available to Level 40 trainers. It will slowly roll back to lower-level trainers, but you’ll have to be at least Level 5 to use the new feature.