Hello.
I kept getting this error when drag and dropping a “helicopter.FBX” file (FBX 2014/2015), exported from 3ds Max 2017 SP3. It was a skeletal mesh, with stubby bones set up at the rotors and parented to a central bone.
I even enabled a “Show Redirectors” filter in the content browser, but I didn’t see anything in that folder (I was expecting some sort of “ghost” file or a reference of some kind).
Edit: A few minutes after I started writing this, I tried dropping it into a different folder this time (into the “Textures” folder instead of the “Meshes” folder), and the import window showed up this time. Hmmm… What, exactly, did I do wrong the first time? I just know it’s gonna bother me. I mean, I wasted half an hour googling for a problem that just doesn’t make any sense. Is this a bug in UE 4.17.1?