Material export for Blender's glTF exporter only works for Cycles materials at the moment.

And even then it requires a specific node setup as mentioned in the [user documentation][1]

Future updates to support EEVEE material node trees is planned but unavailabe at the moment.


  [1]: https://github.com/KhronosGroup/glTF-Blender-Exporter/blob/master/docs/user.md