You must enable the APIs required for Britive to read user, role, and group information from the GCP. The APIs should be enabled on the project where the service account is going to be created.

Log in to the GCP Console with administrative privileges.
Enable the following APIs by clicking these links:
- Cloud Resource Manager: https://console.developers.google.com/apis/library/cloudresourcemanager.googleapis.com
- IAM: https://console.developers.google.com/apis/api/iam.googleapis.com
- Directory Service: https://console.developers.google.com/apis/api/admin.googleapis.com/overview