Just tested with the latest version of TAdvTaskDialog V2.1.0.3 (in the new TMSVCLUIPackSetupReg.exe V10.3.0.0) and I get the same result. I've tested in another project, and again I get the same error. Tested with the app on Rio 10.3.3 on another W10 PC, and again the same error.
The TAdvTaskDialog function is pointing to TaskDialog.pas (5052) which is the correct function location, so I'm not sure why I'm getting this error. I can only think there is a conflict with another component, although a TAdvTaskDialog component works fine.
Thanks, Andrew