Your https:// redirects to http:// and port 80 isn't open on your origin so the connection times out. Check for redirects in page rules, redirect rules or on your origin that do that.
The https:// -> http:// redirect has now gone since I posted. There is now a straight timeout when Cloudflare tries to connect to your origin. Is your SSL/TLS mode set to "Full (strict)"? https://dash.cloudflare.com/?to=/:account/:zone/ssl-tls