Can't import Blender rig as skeletal mesh

I have a mechanical leg that I’ve rigged (with IK) in Blender that I want to import into UE5 as a skeletal mesh and build a control rig for. I’ve looked at just about every tutorial out there on how to do this, but every time I export my armature + the mesh, it just imports all the parts as separate static meshes, and doesn’t even import the armature at all. I don’t know what I’m doing wrong. Here’s the link to my blender project: test.blend - Google Drive