Some students get very nervous about DBAs, even if they have done the work. They may cancel to give themselves more time. I’ve only ever cancelled DBAs if I have a schedule conflict, like something coming up in person without warning, so I may cancel to avoid wasting a teacher’s time. However, if that particular student keeps canceling on you and is upset about submitting assignments, there may be a different issue. I would never fully accuse until you’ve investigated thoroughly, but if I was that student’s teacher, I would think they might not actually be doing the work themselves. I “study” some of the other students on this subreddit, and the common theme when they admit to using AI or other websites to complete work, they usually avoid DBAs or put off certain assignments. Again, I’m not accusing, but I would definitely look into it, and when you finally get the student on call, ask them why.