I had the same problem, this solution, suggested by Peter in the forum, solved my problem: https://forum.reallusion.com/FindPost539151.aspx
For anyone who might encounter this going forward, reinstalling iClone seems to have fixed it. It is possible this was originally caused by moving (via Move Location open in Content Manager popup menu) much of my content to a different drive, to free up space on C:, or it might have just been a side effect of one of many 8.x updates being applied. I did some research of the related files and their locations before reinstalling, and things seemed to be as expected. It would have saved a bit of time to just reinstall from the beginning. YMMV, but the earlier comment from 9/15 was not relevant to fixing this for me.
Activate facial profile editor "edit expressions" for your CC3 avatar, then locate extended facial profile in the content window: make sure "template" and in the item list, "all" is selected, then in the search bar, type in extended , right click on "CC4 extended facial profile" in the list and choose "find file" Copy the folder address, switch to facial profile editor, choose "Load" (folder icon under Edit Expressions" and then paste it into the address bar, hit enter. The file location will now show you the "CC4 extended facial profile" file to load.