If you have created a self sign-up group within your course, you can message students who have not yet signed up for a group and remind them to do so.
Open Group Set
Click the Settings icon , then click the View User Groups link . Or click an existing group set .
Confirm Group Creation and Options
Click the name of the group set you want to view . Verify that self sign-up is enabled for the group set .
Message All Unassigned Students
To send a reminder to students who have not signed up for a group, click the Group Set Settings icon , then click the Message All Unassigned Students link .
Message Students for Self Sign-Up
Canvas will populate the recipient list with the names of students who have not yet joined a group . Type your message into the text area . When you are finished with your message, click the Send Message button .