Sometimes there is lag time between the time when you "Create Group" in the actual Canvas Assignment (Assignment Group portion) and when it shows up as an option under "Unassociated" during the "Sync SIS Categories" process. Sometimes, not always, it takes a few minutes for the new Assignment Groups to populate so you might have to wait for the options to show up in the Association drop-down menu. Usually they will appear in the time it takes to stretch your legs and get a quick drink of water. Leave the Sync SIS Categories page, take a mini break and then go back in using the skinny snowman. They should be there. In a few cases I've seen it take overnight before they show up, but thet's usually rare and at busy school times like back-to-school in August or January. I hope this helps.