Hi!
First, apologies for the newbie Q, I checked the manual & FAQ first.  :\
I bought some assets from the store, and I'm having trouble getting them to work with CC3.  I dropped the .iAvatar file onto my CC3 project, and CC3 asks me if I want to Load Avatar or Replace Costume.  I then get an error message that No standard/non-standard character is picked.  I click OK, and then the creature appears nicely in CC3 behind the dialog boxes, complete with Actor & Actor parts in the Modify panel.  I then get an error message "Failed to load the file. Character Creator supports CC character only."  My creature then disappears and I go back to the default new project.
Character Creator 3 lists .iAvatar files directly in the File -> Import menu as a supported file type.  I have tried several files and get the same message.
I'm on CC3 3.04.1442.1, 32GB RAM, 1080 Ti, Windows 10.
Am I missing something?
Thanks!
-Will