Thanks guys, it was a user error. The export was correct, but I made a mistake in Unity with some animations. I now retargeted those motions to a new mixamo T-Pose avatar, and everything works.

I'm not at my computer, but I'll try to help.

After setting the rig to humanoid, setting avatar definition to create from this model, and applying, I always have to go into the avatar configure mode and enforce the T-Pose. Unity has documentation on that process.

If you are doing all that, what animations are you trying to use from the asset store? Some older animations are designed to work with the legacy animation system and some are designed to work with custom animation systems on the store.

What version of Unity are you using?

I have yet to get CC3's Unity export to align the bones correctly, but haven't dug into it much because enforcing the T-Pose in Unity works for me.

Edit: Can you take screenshots of your CC3 export settings and your import settings > Rig tab? With that information, someone in this forum should be able to help.

I don't use Unity. And I am no expert. In 2019, I found on Reddit, all of the Animation packs from Mixamo.
I saved the over 4GB file on my PC. I was able, with God's help, to convert over 2300 Mixamo motions to iClone.
If you need those FBX motions, here is the link to the Mixamo FBX  for Unity and BVH motions.  Download over 2400 + Mixamo Animation Pack Motions for Unity and 3DS Max + BVH and FBX - YouTube
As I said, I am no expert, and I thank God for helping me convert them. If you can send your character to iClone, you have over 2300 Mixamo motions converted for use in iClone.
If you have 3DXChange, click on the Scene Tree bone on the right and it will be highlighted on the bone of the character. Do that for the hips to the head, and you will get the right bones.
I hope this helps you.
A link I found with God's help. Importing an Animated Character Into Unity 3D (tutsplus.com)

Hi,

I have the same problem. If you try to apply mixamo animations to a cc3 avatar in Unity it gives an error message: "Transform "pelvis" for human bone "Hips" not found."

Sorry for circling back to this; but, would you happen to know of any videos or documents that go through the process? I have been poking around YouTube looking for some step-by-step tutorials and haven't found anything helpful.

Thank you.

Hmmm, ok. I didn't know that was possible. Thank you for this information. I will hunt down some information that goes through this process and give it a go.

Have a great day.

I'm a noob BUT if the bone names don't match.
I'm going to give my best quess that you might need to use 3D xChange to retarget the skeletons of the animations so the bone match up

Hello and thanks for reading my post.
I have been running into an issue that I hope someone could shed some light on. It seems that the rig that comes with characters out of CC3 are not compatible with a lot of animations that are used in Unity. I have tried to use several animations from the Unity asset store and every time I go to set the animation as "Humanoid" and select the Avatar Definition that comes out of CC3 with my character, I get errors. The most common error regards some kind of mismatch and "hips" being missing. Sorry if this isn't clear; but, I am not in front of Unity at the moment. 

Has anyone else found that they constantly run into issues when using animations from the asset store with the CC3 character? The only animations that I have been able to use in my project are the ones from Mixamo. But, that is only after I retarget the animations to use the Mixamo rig and not the one that comes out of CC3.

Has anyone else encountered this? Does Reallusion know/care about this? Does anyone know what the root problem is and if there are any workarounds?

Thanks in advance.