Link
https://glitch.com/edit/#!/internal-electric-shear
I downloaded the unicorn from sketchfab and converted blender file to .glb. For some reason, animation mixer is not triggering the animation. I tried putting my glb file in other online viewers and they run fine there. The animation I am looking for is called Run but nothing is working.
Animation-mixer you used is not a default feature of a-frame. It's a part of aframe extras by donmccurdy
<script src="https://cdn.jsdelivr.net/gh/donmccurdy/aframe-extras@v6.1.1/dist/aframe-extras.min.js"></script>
also use correct name in animation mixer attribute exactly same as mentioned in sketchfab website
<a-entity gltf-model="./unicorn.gltf" animation-mixer="clip:walk">