Configure Nginx as reverse proxy with upstream SSL

Solution 1:

I found what was the error, I needed to add proxy_ssl_session_reuse off;

Solution 2:

In my case, I was trying to reverse proxy a website behind Cloudflare. I got the same error in /var/log/nginx/error.log. I tried many solutions and this one worked for me:

proxy_ssl_server_name on;

yes even it's 2019 now some services still need SNI to distinguish among hosted sites.