Custom error preview failed

Action argument is mandatory.

• target: one of
  • cf-error:1000s
  • block:ip-ban
  • block:rate-limit
  • block:client-auth
  • block:basic-sec-captcha
  • block:country-captcha
  • block:waf
  • block:iuam-basic
  • block:managed-challenge
  • cf-error:500s
  • always-online:no-copy
  • phishing:warn
  • regulation:block
• url: custom template URL to fetch (optional, uses default template when omitted)