After you upgrade Dynamics 365 organizations to Dynamics 365 (online), version 9.0, please also make sure to upgrade the existing Field Service and Project Service Automation solution to the latest and greatest version; this ensures functionalities work as expected and allows you to try out new capabilities introduced in the new release.
To update to the latest Field Service, Project Service solution, visit the Admin Center for Dynamics 365 online, and head to the solutions page to install the update. For details, refer How to Install, Update a Preferred Solution
Devices (using Dynamics 365 App from store)
Devices (using Field Service app)
For more information:
Dynamics 365, Field Project Service Team