Try to restart Blender, if that doesn't help, restart your PC to update the System Variables. Then Blender is able to access the optimizer.

Inside the texture panel, you get a list of all the textures in your scene. This allows you to batch scale textures per object, per material, or for the whole scene at once. This is useful to see what resultion you really need for your final web export because you can see it right in blender without needing to export your scene.

Try to update Node.js to the newest version. If that doesn't work send me a screenshot of the console after pressing the button.