Some enterprise websites (for example, IIS, SAP etc.) require the user to log in with a certificate. Usually, on such sites, a pop-up dialog box asks the user to select a certificate to authenticate themselves (see an example below),
However, in some cases, instead of showing the certificate selection dialog box, the user may see a '404: Page Not Found' error.
The solution is to disable monitoring of the site/domain/IP from the Monitoring Settings screen:
Click the Gear icon near the top right corner of the dashboard and select Monitoring Settings from the pop-up menu.
Click a monitoring profile you want to change or click the Default settings profile to change the monitoring settings for all users.
Click the small Gear icon near the right side of the Websites row.
Enter the website address/domain/IP in the DON'T MONITOR WEB TRAFFIC FOR THESE IPS field and click the APPLY CHANGES button: