Just do it in Nifskope. I do.
Huh? Doesn't compute.
@PhiniusMaster: I don't remember the exact procedure, or which version of NifTools I ended up with. It's confusing because the version profiled on the NifTools download site is in fact not the version we need.
However, I assume you found the correct version as I did using the needle in a haystack method.
The installer (as I recall) asks which version of 3DS Max you want to install the tools for and places the plugin where it should go. In your case, perhaps that did not happen properly.
Do you have multiple versions of 3DS installed? Did you select the correct version/s?
It sounds like you are close to success. I encourage you to pursue this further. It can be done.