Technical Tip: 'Revocation information for the security certificate for this site is not available' message from Windows alert

On rare occasions, end users may see a message pop-up from Windows:

• This pop-up is harmless and happens when the endpoint temporarily cannot reach the Certificate Revocation List (CRL), also known as the 'certificate checking server'.
• This can occur intermittently due to network conditions such as ISP restrictions, firewall or proxy behavior, DNS resolution issues, or brief connectivity changes (for example, switching networks or resuming from sleep).
• It does not indicate a security issue. End users can safely select 'Yes' for the prompt to disappear.

To deep-dive into the root cause of this pop-up message:

1. Check the CRL URL when the same prompt appears, select 'View Certificate'.
2. Go to details, look for: CRL Distribution Points, or Authority Information Access.
3. In the network environment, ensure that:

• The URL is reachable from the endpoint.
• Firewall allows: TCP 80 / 443 towards the URL.

Below is a workaround to completely prevent this pop-up message:

1. Go to Start -> Internet Options.
2. Go to the Advanced tab, uncheck the box for 'Check for publisher’s certificate revocation'.

3. Select 'Apply' and select 'OK'.
4. Reboot the computer for the changes to take effect.