Twitter card `ERROR: Failed to fetch page due to: ChannelClosed` pitfalls behind Nginx proxy

Twitter seems not to accept my newly composed wordpress behind nginx with error code ERROR: Failed to fetch page due to: ChannelClosed

Using tcpdump -i eth1 -X -e -w test.cap on my psychz VPS. it gets

Sounds the handshakes return with different SSL version. ssl_ciphers 'ECDHE-RSA-AES256-GCM-SHA512:DHE-RSA-AES256-GCM-SHA512:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:!3DES'; from did not work. So, eventually, I found I didn't switch on the Cloudflare full encryption. Everything is good.