With Blender 2.80 Beta released there where many changes.
From v1.9.0 of this addon will only work with Blender 2.80+ (and viceversa).
For Blender 2.79 download v1.8.5
Blender Toolshelf, an addon for Blender to:
Import/Export XPS Models, Poses.
Main Features:
- Imports and Exports XPS/XNALara models with armature.
- Imports and Exports Poses
- Imports and Exports Custom Normals
- Creates Materials on import
- Easily set a new rest pose for the model
more info at: http://johnzero7.github.io/XNALaraMesh/