I had an issue where Roll Call appeared to be broken. I had an instructor who wanted to use it but couldn't get it to activate. I noted it was a UW supported LTI app here (https://kb.wisc.edu/page.php?id=65466 that claims "By default, Attendance is included in Canvas as a non-submission graded assignment worth 100 points. The display grade is set as a percentage." This appeared to be untrue in my course. There is no Assignment for Attendance by default.
I dug deeper, and went to the "Attendance" link in the Canvas menu. It appeared my browser was blocking cookies. So, as suggested, I tried launching the tool in a new window. A new window launched and the Panda unicycled on it for the 5 minutes I waited. I checked back under Assignments. Still no new attendance assignment...
Here's a screencast of what I did: https://youtu.be/4byhbJRnaWI
It turned out that I was enrolled in my course both as an Instructor and as a Student, and the two roles were competing to access Roll Call, which apparently confused the poor Unicycling Panda. I could not, however, "Delete" the Student Me —
However, I could "Conclude" myself, then refresh, and I was gone. And Attendance started to work for me as expected.