ruby on rails - Restarted instance causes cloudflare error 521 -

ruby on rails - Restarted instance causes cloudflare error 521 -

i had running rails application on amazon instance via passenger + nginx cloudflare enabled.

i restarted instance on online amazon console right-clicking "reboot". whenever visit site using dns, gives me 521 error stating web server down. however, if visit through ip address directly, works.

i read in few places cloudflare may have been blocked. can identify blocking cloudflare's requests?

that sound @ amazon blocking our ips. have reached out them? cloudflare's ip ranges.

ruby-on-rails nginx amazon-ec2 passenger cloudflare