When you click on the calendar icon, it drops down selections to check off for “Today” and for the six previous days. I just clicked on my daughter’s assignment like this, and the drop-down goes back to Tuesday of last week. If you try it now, you should be able to check off last Tuesday just above “Add Previous Date,” and then you can click on that to add last Monday.
If it’s not showing the previous six days when you click on the calendar icon, you should get in touch with the SCM Team via a contact form, and they’ll take a look at what’s going on.
HTH.