Safari blocks cookies which prevents anyone to log in. It would be great if you could find a way to enable users to log in without disabling Safari's cookies blocker every time. I wonder why Canvas' log in page is considered as a cookie...
Unfortunately, @JBMaurice , Instructure Canvas does not have influence or control over how Safari designs its security measures. For those users who do not wish to disable Safari security features, we recommend using Chrome or Firefox for a seamless experience. We document the Safari situation here.
If you'd like to learn more about the relationship between authentication and cookies, here's an explainer
