We understand that there is an error page for a website you are trying to access that's titled "Your connection is not secure". The article What do the security warning codes mean? includes steps you can follow.
However it seems a little more troubleshooting is needed to help resolve this thread. Follow the steps below to collect the Certificate Error troubleshooting information.
Note: Please be aware that the certificate keychain may or may not be unique. If this is a self-signed certificate please take note to remove the information below "--BEGIN CERTIFICATE"
- From the error page pictured below look for the error message.
- Click on the "Advanced" button and it will show the error link.
- Click on the error link and you will be taken to a page that you can copy the error text to the clipboard. The image below has blocked out the certificate for this example.
Other resources to compare errors: https://badssl.com/