Pre-rigged character's head does not animate when I upload to mixamo

Ok so I have my character I rigged in blender. He poses correctly in blender and he will import and animate in mixamo for the most part, but his head won't move in the animations. It is like he has a neck brace on. Here is a screencap of the bone hierarchy in blender.

I suspected that it had to do with the backpack bone (which is a sibling of the head) that I had for adding a bouncing motion to the backpack after I get the base animations from mixamo. So I removed the backpack bone and tried uploading it that way to no avail. What should I try next? Big thanks to anyone who takes the time to read my question.

P.S. Bonus thanks to whoever can help me understand why zipping my .fbx and my .png texture before uploading does not result in my character having textures in the mixamo preview.