Problem

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When attempting to login to a Duo-protected application on iOS or macOS, the Duo prompt doesn't show, and instead the following error message appears:

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

You may see a gray box appear instead of the Duo prompt in some cases. 

Cause

• This issue may happen if Javascript is not enabled in Safari.
• This also may happen if you have an MDM on the device, such as JAMF, which could be preventing Duo from displaying. 
• Content restrictions on the device may also prevent the prompt from appearing. 

Solution

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For 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.
   
   • If you do not want to fully disable content restrictions, you can allow duosecurity.com within the Content Restrictions page
     on the iOS device.
     
     
     
     
   • If you are opening Screen Time for the first time, you will be prompted to set up the phone for either yourself or a child, and have the option to set a passcode.

For iOS 11 or older:

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

For macOS 10.15 (Catalina) or higher:

1. Open System Preferences
2. Navigate to Screen time > Preferences > Content and 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 Allowed Websites Only list on macOS.