"The error message denotes that there is an error somewhere in SSL/TLS handshake. In short, the cURL error code 35 denotes an SSL connection error. The error can be due to an outdated cURL package, connection errors or else a version mismatch between the PHP cURL and SSL protocol of the end server"
Make sure your firewall does't block our IPs
For more info http://support.simplebackups.io/en/articles/4522830-simplebackups-ip-addresses-firewall
Make sure your cURL version is up-to-date
Check your OS update method for upgrading cURL package.