why don't I see a redo panel?

As an exercise, I tried writing an operator that would align vertices of a mesh in edit mode.  The code works - except that I don't get a redo panel that allows me to set the values of my properties.  What do I need to do so that the redo panel appears?

Note that I tried the example operator from https://docs.blender.org/api/current/bpy.props.html, and it worked  (after fixing a python scripting error) - and I can't really see any difference between that and my code.  Maybe something about my identifiers or registration?

Thanks for any help - here is a copy of my operator:

import math

import bpy

import bmesh

class AlignVerticesOperator(bpy.types.Operator):

    """Align selected vertices"""

    bl_idname = "object.align_vertices"

    bl_label = "Align Vertices"

    bl_options = {'REGISTER', 'UNDO'}

    x_align = bpy.props.BoolProperty(name="X align")

    y_align = bpy.props.BoolProperty(name="Y align")

    z_align = bpy.props.BoolProperty(name="Z align")

    def execute(self, context):

        # when we are in edit mode,

        # at this point context.edit_object is the object data (not the mesh)

        # and the 'data' attribute of that is the mesh data

        mesh_data = context.edit_object.data

        # to work with the mesh_data, we copy it into a bmesh data structure

        # manipulate it there and then copy it back into the object mesh

        bmesh_data = bmesh.from_edit_mesh(mesh_data)

        xa = self.x_align

        ya = self.y_align

        za = self.z_align

        # what is the active vertex?

        select_sequence = bmesh_data.select_history

        actv = bmesh_data.select_history.active

        if not isinstance(actv, bmesh.types.BMVert):

            # the active selection is not a vertex

            return {'CANCELLED'}

        # align the positions of all selected verts

        loc = actv.co

        for vv in (vv for vv in bmesh_data.verts if vv.select):

            if xa:

                vv.co[0] = loc[0]

            if ya:

                vv.co[1] = loc[1]

            if za:

                vv.co[2] = loc[2]

        # copy the mesh data back to the object

        # (this happens automatically when switching back & forth between object & edit mode)

        bmesh.update_edit_mesh(mesh_data, loop_triangles=True, destructive=False)

        return {'FINISHED'}

def menu_func(self, context):

    self.layout.operator(AlignVerticesOperator.bl_idname, text=AlignVerticesOperator.bl_label)

# Register and add to the "vertex" menu

# (required to also use F3 search "Simple Object Operator" for quick access).

# we got the menu name by hovering over the menu (with Python Tooltips turned on)

def register():

    bpy.utils.register_class(AlignVerticesOperator)

    bpy.types.VIEW3D_MT_edit_mesh_vertices.append(menu_func)

def unregister():

    bpy.utils.unregister_class(AlignVerticesOperator)

    bpy.types.VIEW3D_MT_edit_mesh_vertices.remove(menu_func)

if __name__ == "__main__":

    register()