A machine catalog's minimum functional level establishes the minimum VDA capability accepted by the Broker service. If the administrator selects a catalog functional level higher than that supported by the installed VDA version, registration is rejected and the machine can report a FunctionalLevelTooLowForCatalog condition. The corrective action is to upgrade the VDA or reduce the catalog's minimum functional level to a compatible value. Citrix Health Assistant is a diagnostic utility; not running it cannot cause the failure. An invalid naming scheme normally prevents successful machine or computer-account creation during provisioning. Similarly, an unavailable required snapshot would interrupt MCS catalog creation rather than create machines that later fail only at registration. Citrix confirms this precise registration condition and its remediation in CTX239687.

Study Guide Reference: Supporting and Troubleshooting Citrix Virtual Apps and Desktops --- VDA registration and functional-level compatibility.