You need to ascertain why Marc did not receive his reports. What should you do?

The ReportServerService_<timestamp>.log file is the SSRS service trace log that records subscription processing, delivery attempts, and errors in detail. When a user does not receive a scheduled or subscribed report, this log captures the exact delivery failure reason including delivery extension errors, rendering errors, and scheduling problems. It is the primary diagnostic file for SSRS report delivery issues.

The Windows registry stores configuration settings, not runtime error logs, so it will not contain information about a failed report delivery event.

The Windows Application Event Viewer may log high-level SSRS service crashes but does not contain the detailed subscription and delivery error information needed to diagnose why a specific user's report was not received.

SQL Server engine logs record database engine activity such as startup and query errors, not SSRS subscription delivery failures, which are handled at the reporting services layer.