If, when going to the pages of Examus or testing systems, you encounter this error "Connection is not secure" with the code NET::ERR_CERT_DATE_INVALID and you are using OS X El Capitan, then the reason is the use of an outdated DST Root CA X3 root certificate, which expired on 09/30/2021



This affects the availability of many sites on the Internet. To fix the problem, it is recommended to update to macOS Sierra 10.12.1 or later. Learn more about the update on the Apple website.

An alternative is to manually install the root certificate. This method does not guarantee 100% uptime of sites, for a guarantee it is recommended to update the system!

Follow these steps:

  1. Download a fresh certificate from the website of its publisher (Let's Encrypt) using this link . When you try to download, you can see the same window with an error, click in it "Additional" - "go to the site letsencrypt.org (insecure)". 

  2. Open Finder - Downloads.

  3. Double-click the left mouse button on the isrgrootx1.der file and in the dialog box - Add:



  4. Open the Keychain Access application (after the previous step, it can be minimized. Or use the search in Finder - Keychain Access) and go to "Categories" - "Certificates":




  5. Double-click the left mouse button on the ISRG Root X1 certificate and in a new window, click on the triangle to the left of the "Trust" inscription

  6. In the "Options for using the certificate" item, select "Always trust" and then close this window (red button). For confirmation, you may need to enter the computer administrator password:




  7. Close all windows and browser. Then try to visit the problem page again.