There are a few reasons why you might not see some of your schoolwork in your Today planner.
1. Some classes are not enabled
Verify the Google Classroom settings in your Profile menu under Connected Apps. It is possible some classes are not checked.
2. Older items get moved to the Done column
When you first connect your Google Classroom classes, items older than 14 days are automatically marked as Done. This is done to avoid having a ton of old items which were posted earlier. Since Materials and Announcements do not have a Due date, we mark them as Done to help clear up things a bit.
3. Student announcements do not appear in Today
If you or your classmates have the ability to post announcements in a class, these are not displayed in Today at this time.