This message appeared in the Project panel in Templates. At this stage, all I'd done was open the software for the first time. It appeared for other templates, too. Have I overlooked some aspect of the installation?

I checked the Reallusion Templates and Custom folders and all the right headings are there, but without any content.

Because this seems to be an installation issue, I should mention that instead of installing the software on the C: drive, I opted to place it on a different drive, as the C: drive was almost full. This resulted in this structure: X:\Reallusion containing three folders: Cartoon Animator 5, Reallusion Custom, and Reallusion Templates.
My suspicion is that some paths in the software are hard-coded on the assumption of a different structure.

Thanks, I will. What's your folder structure look like? All my other Reallusion programs are on the C: drive.

I've reinstalled CA5, but in the C: drive, and the problem has now been resolved.