Hello @jbarr
Thanks for posting this in the Canvas Community! I apologize that students are showing 0's in all courses. That sounds super stressful.
There might be a few things you can check on this. The gradebook history should show some small signs of what may have caused this to happen. If the grader is listed as "Not Available" it usually indicates that an automated process such as a late or missing policy may have been applied.
I'm not entirely sure if this is what occurred in your courses, but from my personal experience this will usually happen one of the policies was enabled, and the course assignments were published before the due dates on items were adjusted. Sometimes this will happen if a course was copied from a previous year and the due dates were not removed, or adjusted correctly before publishing in the live course.
To save some time and heartache, I always recommend that instructors double check their due dates before publishing anything to avoid issues down the road as the course ramps up and goes into session.
Hopefully this helps a bit!
-Colton