If students submit to a group assignment that does not have an associated group set, those submissions appear as individual submission rather than group submissions. Because this causes numerous problems for students, teaching teams, and Canvas support teams, we would like to see some kind of error message, warning, or other blocking mechanism when students try to submit -- ideally, this would prompt students to reach out to a teaching team member who could correct the assignment before students begin submitting.
While I recognize that preventing/delaying a student submission may not be consistent with Canvas's student-friendly approach, the dangers, risks, and extra work associated with the problems caused by this issue warrant considering this idea. In the past, Canvas unofficially supported individual submissions to group assignments, but that is no longer the case and a group assignment without a valid associated group set is essentially "broken."
Canvas currently will not save an assignment if a valid group set is not associated with the assignment:
Why does this happen? Group sets are most commonly deleted as a result of how Group Sets and Group Assignments behave during course copies (including Blueprint courses -- Canvas Release: Blueprint Courses😞 The copied course has a group assignment associated with the default "Project Groups" group set. However, because this copied group set does not include any pre-created groups (see https://community.canvaslms.com/ideas/10709-enable-group-setup-wizard-for-existing-group-sets-resubm...), that group set may be deleted and a new one created, to benefit from the convenience of having Canvas automatically create groups. Even if the group set is given the same name ("Project Groups"), it is considered a different group set and not automatically associated with any assignments. And the end result is a group assignment without an associated group set.
If students submit to an assignment without an associated group set, they essentially submit as individuals to the group assignment -- which is not supported. The expectation is that students will be placed into groups within a group set prior to submission (How do I assign an assignment to a course group?).
This behavior causes numerous problems for various groups:
Problems for students:
Submission is visible only to the group member who submitted the assignment
Delayed grading/feedback, if teaching teams need to correlate students/group submissions manually
Risk of losing credit for a group submission entirely
Problems for teaching teams:
Loss of the ability to use the group grading/feedback functionality
The "disappearing comments" problem in SpeedGrader (comments intended for group members do not display in SpeedGrader if students are not in a group, unless the "grade individually" option is selected, see How do I grade group assignments in SpeedGrader?)
Multiple, possibly different and/or late, group submissions to navigate, if concerned students resubmit because they see the assignment is still due/overdue
Inability to effectively use the "message students who" feature for the assignment
Unexpected and excessive manual work to correlate group submissions and students -- especially for large-enrollment classes (which can be very challenging when there are students who use nicknames that may not obviously match the name in the LMS)
Problems for (local) Canvas support teams:
When we've reported problems associated with this issue to Instructure support, we've been told that individual submissions to group assignments is not supported, leaving our team to address problems locally.
Often the fix requires recreating the assignment, configuring it correctly with a valid group set, and submitting on behalf of students/groups using masquerade. Depending on the size of the course, this can take a great deal of time, and it requires that support teams doing this be root admins.
There are fewer options for support teams without the ability to masquerade, placing a larger burden on students and teaching teams.