If your guest dashboard page uses the Conversion Kit guest portal shortcode and Booking Readiness still warns that the shortcode is missing, your setup is correct. The warning is a false positive.
Why this happens. Earlier versions of the Toolkit’s Booking Readiness check recognize only the core [homerunner-user-dashboard] shortcode. They do not recognize [hrck_guest_portal] as a valid guest dashboard. This is corrected in Toolkit version 3.334.94, which accepts the Conversion Kit guest portal shortcode as a valid guest dashboard page.
What you can do. Update the Toolkit to the current version (3.341.1 or later) from your WordPress dashboard. Once updated, Booking Readiness recognizes your Conversion Kit guest portal page and the warning no longer appears. You do not need to change your page or shortcode.