The Full Configuration interface alerts about unsupported functional levels with "This catalog's minimum functional level is no longer supported. To avoid potential issues, set the functional level to 1811 or later." 

We recommend changing the functional level in the machine catalog to gain access to these lower functional product level features.

1. From Manage > Full Configuration, select Machine Catalogs in the left pane.
2. Select the catalog. The Details tab in the lower pane displays version information.
3. Select Change Functional Level.
4. Test and verify the change before implementation.

 

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Problem Cause

If the functional level of a catalog or delivery group is not supported, the Full Configuration interface alerts about unsupported functional levels.
Now 1912 LTSR (1912 EOL:18-Dec-24) is the oldest supported VDA version, so 1811 will be oldest supported functional level. Functional levels below 1811 will have a warning.  

https://docs.citrix.com/en-us/citrix-daas/install-configure/machine-catalogs-manage.html#add-machines-to-a-catalog

https://docs.citrix.com/en-us/citrix-daas/whats-new#november-2022 ​​​​​​​