Proctored exams in edX are offered by a 3rd party vendor called Software Secure. Proctored exams can be completed on Mac or Windows desktop or laptop computers only. You can see the proctoring software system requirements on this page.
If you get stuck during the proctoring process you are welcome to contact Software Secure at 1-844-224-9759, or on their live chat which is available 24/7:
You also might find this article on proctoring in our learner documentation helpful.
Best of luck on your exam!