Which error logs should the administrator be reviewing to determine why the relates service is...

The error log that the administrator should review to determine why the relay service is down is Cerebro.ERROR. Cerebro is a service that runs on each FSVM and provides relay functionality for Data Lens. Relay service is responsible for collecting metadata and statistics from FSVMs and sending them to Data Lens via HTTPS. If Cerebro.ERROR log shows any errors or exceptions related to relay service, it can indicate that relay service is down or not functioning properly. References: Nutanix Files Administration Guide, page 23; Nutanix Data Lens User Guide