Hello, @aeisen 
First, please check the version of Safari you're using (by clicking on Safari at the upper left and then on About Safari) to ensure that you're using Safari 12 or 13. If you're not, you'll need to update your browser to the latest version—and to do that, you'll first need to update the MacOS to the most recent supported version (see What are the basic computer specifications for Canvas?).
If you're already on the latest version of Safari (again, 12 or 13 at this writing), clear the cache and cookies in the Safari browser, close and then relaunch the browser.
Last, try switching to a different browser. Canvas works quite well on a Mac through Chrome, and Firefox works well also. Here's a list of supported browsers: Which browsers does Canvas support? Again, on a Mac, updating the OS is a prerequisite for generating download links to the latest versions of browsers; definitely give Chrome a try.
If this doesn't resolve the issue for you, please contact Canvas Support. General instructions are in How do I get help with Canvas as a student? but your school's support setup might vary somewhat, in which case ask your local IT Department for additional troubleshooting assistance.
Good luck!
