Secure connection failed An error occurred during a connection to live.mozillamessaging.com. security library failure. (Error code: sec_error_library_failure

There's a long correspondence about this here: https://support.mozilla.org/en-US/questions/993843 I advise that you read through it so that you understand the issue. In that case, the root cause was a security add-on that the user had installed: once that was removed Thunderbird operated normally.