Where is the default location for the SQL Agent Job step output file? How do I update it?
If the Job Step runs a Maintenance Plan, then the logging is perhaps being done in the "Maintenance Plan" which is somewhat common. Choose the specific Maintenance Plan (from SSMS -> Management -> Maintenance Plans) that is referenced by the Agent Job, click on the circled icon for "Reporting and Logging" and check the logging location on it as shown in the dialog below: