@KamaleshV It looks like the user is trying to add UI-Kit in the "Component Rulesets" part of a Component. That is not allowed, as PEGA insists that Component rulesets would have to be new rulesets created by the user.
Now, there are certain rulesets which are created by PEGA, and they are not allowed as part of the Application rulesets within a component. You can however add them in the Pre-requisites part of the component.
I am not sure whether above workaround works. Do let me know , but there is no scenario in which this would be desirable.