Hello: I am using the CC4 and want to use it with Unity (latest version).  I create an HDRP project and import my CC4 character as per web site instructions.  All works fine.  Problem is the character is of poor quality.  Hair does not look natural, face looks somewhat cartoony, and the shadows around the shoulders flicker getting dark and lighter.  When  I save the project and reopen all the materials are pink.
When I export the character for Unreal and import in Unreal all works great.
Problem is I use Unity and not Unreal engine.
Anyone have any ideas as to what is going wrong.
Thanks in advance for any help

Are you sure you're using the prefab that gets generated by the Import process, and not the original raw FBX? 
For example, if I add a CC4 character as "Kyle.fbx" to my project, and I use the importer to import it, I'll see a new folder called Prefabs in the same directory as Kyle.fbx. Inside of Prefabs will be a prefab called "Kyle.prefab". That's what you need to be using, rather than the original Kyle.fbx. Otherwise, the materials will be wrong, and the meshes won't be extracted properly.

If that's not the issue you're having, I'd suggest being more specific about what you're seeing, and ideally include some screenshots.