Since you are just getting started, I would recommend taking time to review the various account level reports. These reports are easy to run, don't require any additional set-up (other than making sure the appropriate users have permissions to access them), and provide a good starting point for Canvas Reporting. Depending on the question you are trying to answer, a single report may be all you need, or you can use VLOOKUPs/XLOOKUPs to combine data from multiple reports.
For the example you provided, you might consider using the Zero Activity report since it shows all enrollments for a term, where the student hasn't visited the course since the specified start time.
After taking some time working with the Canvas Default Account Reports, if you find other things you want to generate reports for that can't be easily done with them, I would recommend checking the Canvas Community to see if it has already been asked before. Someone else may have shared an approach for how they created a custom report that provides that information. If you don't see an answer for the type of report you are looking for, you can make a new post and someone may be able to make suggestions. Canvas Data and/or Canvas APIs are often used when looking to make a custom report.
