When I load my custom character into Mixamo and place the points, I get a message saying "Unknown Error while generating motion." It's like Mixamo doesn't recognize my model as a riggable character. I realize it may be hard to tell from just a screenshot, but on first glance can you tell what it is about my model that is causing issues? The thumbs look reversed here, but they are correctly positioned. Also, I tried this model with different hands, thinking they were the problem--but no results. Granted, it's clumsily built. But I just ran this off as a prototype for something in AR. Wondering if my construction method in C4D is the problem, but I haven't had too many problems so far.
the thumbs are correct mate which means your file (assume Fbx) is reading wrong and turning the head around to face behind... I would convert this model to wavefront Obj, upload that to rig the bones and adjust my work flow from that point