Go to HTTPS Cloudflare SSL Settings
{
  "error_code": "HTTPS_REQUIRED",
  "message": "HTTPS is required.",
  "hint": "If you are using Cloudflare, set SSL/TLS mode to Full.",
  "required": {
    "protocol": "https",
    "cloudflare_ssl_mode": "full"
  }
}
If this page keeps showing on Cloudflare, check that SSL/TLS mode is set to Full (not Flexible).