I'm just updating this topic because Monica from Canvas Support finally found the correct solution.
Apparently, I was logging in to canvas.instructure.com whereas I should be logging in to k12.instructure.com.
Here are the instructions she gave me:
When the "Find my school" screen comes up, type in "K12" and click "go". You will then see the login screen asking for your credentials. At that point, you can enter the same credentials that you have been using. HERE is a recording of this process. Once logged in, you should see your to-do list functioning as expected and the submission files will be visible.
I can't believe that I had to do that to login correctly because nobody would have guessed you had to do that. It doesn't say so anywhere. In fact, instructions online say to use "Free Canvas Accounts" when choosing your school. I wonder how many other people gave up on the app because they never knew they had to type "k12" and hit go. So very weird!
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.