I’m deploying SSL to one of my domains and some of his subdomains…
I was forcing any request to HTTP to be redirected to HTTPS with NGINX but…. it was causing a loop!

I had to disable the redirect at nginx and do it with Cloudflare Page Rules.

Sources: https://support.cloudflare.com/hc/en-us/articles/218890817-Fixing-redirect-loops-when-using-Flexible-SSL