Hello there, @peppele ...
Give this a try. Click on your "Studio" button in your global navigation. Then, click on the three-lined hamburger menu icon in the upper left corner of the Studio dashboard. Scroll all the way down, and you should see a "Studio Settings" link. On the screen that appears, you'll see five tabs of information...the first is "Permissions". There should be a row for "Add video quizzes to media", and you can turn this on/off for both Teachers and Students. There is no "Save" button...as any changes you make should be immediate. This Guide gives a good summary, too: How do I manage user role permissions for a Canvas Studio site as an admin?.
I hope this will help out a bit. Sing out if you have any other questions...thanks! Take care, stay safe, and be well.
My permissions were enabled, but it still didn't work for my teachers. I had to call Canvas support and they were able to get it working for me.