The main causes of the "This site is not secure" error page are as follows:

1. Certificate mismatch error

Error message: SSL_ERROR_BAD_CERT_DOMAIN, ERR_CERT_COMMON_NAME_INVALID

The above page is an error message indicating that the domain and certificate of the requested server do not match.

Please check if a certificate matching the domain is installed on the server you are using.

2. Certificate expiration error

Error message: SEC_ERROR_EXPIRED_CERTIFICATE, ERR_CERT_DATE_INVALID

The above page means that the SSL certificate has expired.

You need to issue a new certificate and replace it.

3. PC date error

Error message: ERR_CERT_DATE_INVALID

The above page is an error that occurs because the PC's time setting is not set correctly.

Please apply the time setting automatically and try connecting again.

4. Certification authority reliability issue

Error message: ERR_CERT_AUTHORITY_INVALID

This error occurs when there is no list of certificates for the certification period or when the certificate is issued by an unknown agency.

Please check if the local certificate information is set correctly.

In the case of an internal network, the root certificate within the server requires communication to be certified by the certification authority (CA),

so the URL and port of the certification authority must be opened in the firewall.

5. Certificate Revocation

Error Message: ERR_CERT_REVOKED

If an error occurs because the certificate in use has been revoked, you should contact the issuing agency or issue a new certificate and reinstall it.