Thanks to some dogged investigation by @oisin650 it seems that the FAA only retain charts for the current and previous AIRAC cycle, e.g. at time of writing, 2201 and 2113. The CL-650’s digital charts function uses the AIRAC cycle associated with installed custom nav data (if present), or default nav data otherwise, to fetch the charts from the FAA. (Which makes sense, one would want charts to match one’s nav data.) However, this means that if one only has default nav data then the FAA chart function is unavailable, because X-Plane ships with nav data from 2018 and these charts have long ago been removed from the FAA’s digital chart service. The solution right now is to have up to date nav data, this is available to purchase from Aerosoft or Navigraph. (I highly recommend the Navigraph Ultimate subscription that gets one access to global Jeppesen charts in the avionics instead! #notsponsored)