SEO Snapshot requires two CRON tasks to be set up in order to generate reports.
wget -O /dev/null http://your-seosnapshot-url.com/cron/urgent
wget -O /dev/null http://your-seosnapshot-url.com/cron/current
You can run these tasks every minute, or set the schedule for however long you're prepared to wait for a report to be generated.
Please see the attached Setup Requirements document for an example screenshot of a well-formed CRON task.