The Error Log - Critical Error (severity level lower than 20) alarm becomes active when Spotlight Enterprise detects a new error message that contains one of the following log entries: 'Severity: 17', 'Severity: 18', 'Severity: 19' in the SQL Sever error log.
When this alarm is raised view the SQL Server error log around the alarm time. (Amazon RDS for SQL Server | Error Log drilldown)
Note: Use the Spotlight Client Configure | Error Log Entries to define and edit the alert rules that Spotlight scans the SQL Server Error Log for. Spotlight scans the error logs at the configured frequency. If you make changes to the alert rules it may take some time for changes to take effect.