How to fix screen flickering when 802.1X Authentication prompts for network action

Question

I have 802.1X authentication enabled on my domain with a NAC running the authentication and onboarding. I have multiple computers experiencing screen flickers every time the prompt for network action pops up. The flickering alternates between black and white screens rapidly and renders the computer inoperable. I am forced to restart the computers while the ethernet is disconnected to stop the flickering and disable the NAC configurations to stop the switch from prompting for authentication if I am to connect to the network without flickering. I have not found any documentation or suggestions online to deal with this error. I have tried running the latest updates on these computers but still no t working

Answer 1

Hi，@MbauWoodz 

Depending on your description, there can be several reasons for this issue. 

One possible cause is that your devices are using Windows Defender Credential Guard, which is a security feature that isolates credentials from the operating system. This feature may interfere with 802.1X authentication and prevent single sign-on (SSO) from working properly. You can try to disable Windows Defender Credential Guard and see if that resolves the issue. You can find the steps to disable by below steps: 

1.If you enabled it by using Group Policy, you can disable it by navigating to Computer Configuration > Administrative Templates > System > Device Guard > Turn on Virtualization-Based Security and setting the dropdown value to Disabled in the Credential Guard Configuration section. 

2.If you enabled it by using Windows registry, you can disable it by deleting the following registry keys: HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\DeviceGuard\EnableVirtualizationBasedSecurity and HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\DeviceGuard\RequirePlatformSecurityFeatures. 

3.If you enabled it by using the hardware readiness tool, you can disable it by running the tool again with the /disable parameter. 

Another possible cause is that there is a problem with the certificate that is used for 802.1X authentication, such as invalidity, expiration, chain verification failure, or revocation check failure. You can try to check the certificate status and validity on both the client and the server side, and make sure they are trusted by both parties. You can also try to renew or replace the certificate if it is expired or invalid. You can find more information about how to troubleshoot 802.1X authentication issues in the link below. 

802.1X authentication issues troubleshooting - Windows Client | Microsoft Learn 

Hope the information is helpful. 

Best Regards, 

Hania Lian