You need to have a KeyframeSequence instance. This is the raw animation information that gets uploaded to the website and packaged into an AssetId when you export from the animation plugin. Without a KeyframeSequence, you can’t publish any materials as an animation asset.
If it’s not your animation then you will need to ask the creator of the animation asset in question for the KeyframeSequence to upload or create your own. Seeing as you’re using a kit that doesn’t provide raw animation files you will need to create your own animation.