Hi @test,
I make pretty extensive use of the Canvas API (have a script that runs thousands of calls daily), and I don't think I've ever encountered this issue. NXDOMAIN generally means the domain name you're using (school.instructure.com, for example) cannot be found by your local computer for some reason. Are you using an instructure.com domain, or a school/institution vanity domain (like canvas.school.edu)? A couple other questions that could help narrow down the issue... Does this issue occur on one specific computer or all computers? Have you tried a using different internet connection (if that's possible) to see if you get similar results?
Let us know the answer to these questions if you can. Hopefully someone in the community here can offer up some suggested solutions based on your answers.
-Chris