I'm running CiviCRM 4.7.9 on Drupal 7.50. Drupal's cron is running fine every 3 hours, using Drupal's built-in scheduler. I can also run cron successfully manually.
However, I still get the famous error message in CiviCRM saying that cron has never run:
What specifically in the database is this check looking for, and what's supposed to be creating that? Is this likely to be a problem with cron actually not running, or a problem with detecting whether it's run?