Unfortunately, Kajabi won’t let you proxy their services with your own Cloudflare account. This means you can’t add any Page Rules or use any other Cloudflare features that may forward any URLs in that domain.
Rumor has it that Kajabi has very recently set up a way to let users Proxy their domains, which would allow Page Rules to work. I suggest you confirm this with Kajabi, as their own documentation has not been updated to reflect this.