Rbz error installing extension

Trying to install a ruby script posted on this forum to flatten a model to set Z = 0

Saved the script as a rbz file but on install get “Errors were encountered”

Not a ruby programmer, can anyone help?

Script is:

encoding: UTF-8

module SetZEqual0; end
module Author::MoveToGroundPlane

extend self

MENU_TEXT ||= “Move to Ground Plane”

@@loaded ||= false
@@disable_ui ||= false

def move_to_ground_plane(ents)
model = Sketchup.active_model
model.start_operation(MENU_TEXT,@@disable_ui)
ents.each do |ent|
ent.transform!([0,0,-ent.transformation.origin.z])
end
model.commit_operation
end

if !@@loaded

UI.add_context_menu_handler do |popup|

  sel = Sketchup.active_model.selection
  unless sel.empty?
    ents = sel.grep(Sketchup::Group) + sel.grep(Sketchup::ComponentInstance)
    unless ents.empty?
      popup.add_item(MENU_TEXT) { move_to_ground_plane(ents) }
    end
  end

end # context menu handler registrar

@@loaded = true

end # run once at first load

end # extension module

You must first zip the file and then change the extension to .rbz.