521 from cloudflare, but pausing makes site work again

I imagine this started just recently?

Also - could you provide some info:

  • Does your origin server have SSL/HTTPS itself?
  • What is the “SSL” mode in the SSL/TLS app of your sites?
  • Do you have any firewall set up, either at your host or via something like UFW/iptables?
  • Have you already whitelisted Cloudflare IPs?

Also see Community Tip - Fixing Error 502 / 504: Bad Gateway