By default the service edition is logged into the "Local System" account. The service is able to access any network file share the local system account has permissions to access via a full UNC path.
Mapped drives are specific to logged in users and are not shared between users on a machine. The local system account doesn't have access to mapped drives that may be set up in your user account, so you may need to change the service login to something that can login to the remote system. We recommend that you create the same user account on both local and remote systems and set the password to be the same. For example, create a user called CatTools and set the password to be the same on both systems.