Go to the class page, choose 'Actions', then ‘Manage reports’. This will show the progress of any reports you’ve asked for, like this:

• ‘Preparing’ means we’re working on it
• ‘Download’ means your report is available. Click on the button to download it
• ‘Failed’ means that we haven’t been able to generate your report. You can view the details of the errors and remove the report from the list.