You may need to add UVs in Blender, too. In the Mesh tab, add a “UV Map” 
But typically I also use KhronosGroup/glTF-Blender-Exporter. Only one can be enabled at a time.
You may need to add UVs in Blender, too. In the Mesh tab, add a “UV Map” 
But typically I also use KhronosGroup/glTF-Blender-Exporter. Only one can be enabled at a time.