If you are getting a certificate error message, there are few of steps you can take to troubleshoot and solve the issue:
Check your internet connection and make sure it’s working properly.
If using a Wi-Fi connection, make sure you are connected to the proper network.
If the website you are trying to open is secured with an SSL certificate, make sure it is up-to-date.
Clear the cached files and cookies from your browser.
Check that your computer’s date and time settings are correct.
Try using a different web browser.