I have a rigged "house cat" model created for me by an actual 3D artist, and sent to me as an .fbx. It contains the mesh and the armature in a rest pose (A). Later, the artist sent me a second .fbx containing the same armature, but in a different rest pose (B). I need to import pose B from the second file into the first file for armature A.
I have appended the second file to the first (so it now has both armatures), gone into pose mode for B, selected all bones, pressed Ctrl-C, chosen "copy pose", gone into pose mode for A, and pressed Ctrl-V. Nothing happened. Just for good measure I selected all bones and tried Ctrl-V again, but with the same results.
I have linked the animation data between the two armatures, and attempted to use B's animations, actions, pose libraries, and poses on A, also to no effect. I have attempted to use a "Copy Transforms" constraint, but end up with the entire armature A constrained to the size of B's hip bone, and still in the wrong pose.
I am using Blender 2.90.1 on Windows. I have spent four days searching blender.stackexchange.com and the web in general looking for a way to do this, but cannot find a method that works. I could use any hints, tips, suggestions, pointers, or anything at all that could help me get this to work. There shall be many more poses over time for amature A, so I'm really hoping there's a solution easier than trying to manually position A overtop B, especially since I, myself, don't have an artistic bone in my body (horrible pun intended and regretted).
Thank you, Bryon M. Elliott