Robot model not spawning in Gazebo11

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Hi there,

I'm trying to load my TM5-900 robot model in Gazebo11 and I can see the links list on the left box, but the meshes are not loaded. This is my launch file:

    gazebo = IncludeLaunchDescription(
     PythonLaunchDescriptionSource([os.path.join(
             get_package_share_directory('gazebo_ros'), 'launch'), '/gazebo.launch.py']),
         )
    spawn_entity = Node(package='gazebo_ros', executable='spawn_entity.py',
                    arguments=['-topic', '/robot_description',
                               '-entity', 'robot', "-x", "0.0","-y", "0.0","-z", "0.0"],
                    output='screen')

What am I missing? Thanks