You may encounter the following message when accessing some Google websites, such as national domains, GMail, etc.:

Your connection is not private
NET::ERR_CERT_AUTHORITY_INVALID

This issue is caused by a missing GlobalSign certificate in your computer's local certificate store. Please follow these steps to add the certificate:

  1. Use the following link to download the R2 GlobalSign Root Certificate:
    Download certificate
  2. Double-click the downloaded file, and then click Install.
  3. Select Local Machine, and then click Next.
  4. Select Place all certificates in the following store, and browse to "Trusted Root Certification Authorities". Click OK.
  5. Click Finish.
  6. Restart the computer.

Now you will be able to access the affected websites without issues again.

More information is available in the following article:
https://textslashplain.com/2017/10/23/google-internet-authority-g3/