There are a couple of possibilities:
- Please make sure your site is published before sending out Announcements. Announcements cannot be sent from unpublished or concluded course sites. The date and time that a site was published is recorded under Settings >> Course Details tab >> Start date/time. Note: This field can be edited by those who have the Teacher role.
- The notification may have gone into the Spam folder of the students' email, so they may need to check there. Also, if they have email filters set up in their email application, it's possible that some messages may be getting inadvertently caught in that filter, depending on the filter's settings.
- They may have changed their default notification setting in bCourses/Canvas, which, by default, is ‘ASAP’ for Announcement postings and Inbox messages. Please keep in mind that students, as well as all users, have the ability to change the frequency of how often they’d like to receive Announcements, or any notifications from bCourses, by going into their User Settings.
While we can recommend to students that they leave their Notifications Preferences as they are, ultimately, each person decides how often and where they will receive messages sent from bCourses. Therefore, it is important to have a discussion and/or a written statement in your syllabus about your class communication policy so that, regardless of their preferences, they are aware of their responsibilities and alternate ways of contacting your and/or your teaching team should they experience any issues. For instructions on how to set up notifications, please see this Canvas Guide: How do I set my Notification Preferences?
(Related question: Why didn't I get a copy of the Announcement that I posted?)