The University's two-factor authentication provider, Duo, has noted that there is a known authentication issue on Mac and Apple devices. When attempting to authenticate to 2FA-protected sites, some people have gotten the following error instead of the 2FA authentication screen:

You cannot browse this page at "duo.com" because it is restricted.

There are a number of things that you can do to address this error, including making sure Javascript is enabled in Safari and disabling content restrictions.

Make sure Javascript is enabled in Safari

1. In Safari, open Preferences.
2. Select the Security tab.
3. Check to ensure that the Enable Javascript box is checked.

Disabling content restrictions

iOS 12 or newer:

1. Navigate to Settings > Screen Time > Content & Privacy Restrictions > Content Restrictions > Web Content.
2. Uncheck Limit Adult Websites to completely disable content restrictions
3. If you do not want to fully disable content restrictions, you can allow duosecurity.com within the Content Restrictions page on the iOS device. This will allow the Duo Prompt to display even if content restrictions are enabled.
   

Note: If you are opening Screen Time for the first time and haven't set up the feature, you will be prompted to set up the phone either for yourself or a child and will have the option to set a passcode.

iOS 11 or older:

1. Go to Settings > General > Restrictions > Websites.
2. Uncheck Limit Adult Content to completely disable content restrictions.
   

macOS 10.15 (Catalina) or higher:

1. Open System Preferences.
2. Navigate to Screen Time > Preferences > Content & Privacy.
3. Set any Web Content restrictions to Unrestricted access. If you do not want to fully disable content restrictions, you can allow duosecurity.com within the Content Restrictions page on the iOS device or to the Allowed Websites Only list on macOS. This will allow the Duo Prompt to display even if content restrictions are enabled.