What does the error message "Unable to sync" mean? Ing. Oliver Baltz October 19, 2022 19:30 Updated This is an internal error. Please contact our support so that we can analyze the exact cause. Related articles What Microsoft 365 rights/licenses/packages are required to sync contacts? Is sync.blue® an independent, central address book? What settings are required in the Microsoft 365 Admin Center? Comments 0 comments Please sign in to leave a comment.