The Duo prompt required to authenticate a user's login can appear blank on some Windows computers. This is likely due to security restrictions not allowing the Java wrapper to show the necessary information.
First, verify that the issue is in fact as described above. The screenshot below is what you should experience.
Once verified, open Internet Explorer (not Microsoft Edge);
- Head to Tools, then Internet Options.
- Select the Security tab, then Trusted Sites.
- Enter the address "https://duosecurity.com", and then click Add.
- Select the Privacy tab, and enter "duosecurity.com". Then click Allow.
- Close the Internet Explorer browser, and test functionality.