As the TD Manager you have access to "All Classes" without actually being allocated to the class (you're not included as a teacher of the class), apart from the class(es) you teach.
The benefit here is that you avoid getting the emails that teachers send to their students (this can be annoying if lots of teachers are frequently sending emails to their class). The downside is that, for classes you're not allocated to:
1. You can't email the class directly using the class email address, and
2. You can't open the Google Drive folders of students in other classes. You can, however, view up to the 25 most recently edited files via TD.
The alternative is to explicitly allocate you as a teacher of all (or some) classes, which we're happy to do for you. Please submit a ticket to effect this change.