If your institution restricts access to certain URLs, an administrator or someone in IT may need to "whitelist" these URLs to ensure instructors and students can access the service being provided.
Extempore URL for Whitelisting:
*.extemporeapp.com
How do I tell if my institution controls access to certain URLs?
Open this URL in Chrome: chrome://settings/content/popups
The option to 'Add' will be grayed out if your institution controls access.