I tried doing the tutorial for making a simple two wheeled robot with caster, and the model won't show up on my insert tab. I checked the directory, and it shows all the other models, but not the one I created. I tried trying SDF version 1.4 and 1.6. My code is as follows:

    <?xml version="1.0"?>
<model>
   <name>My Robot</name>
   <version>1.0</version>
   <sdf version='1.4'>model.sdf</sdf>

   <author>
        <name>My Name</name>
        <email>me@my.email</email>
   </author>

   <description>
        My awesome robot.
   </description>
</model>

And my actual model.sdf is as follows:

<?xml version="1.0" ?>
<sdf version='1.6'>
        <model name='my_robot">
        <static>true</static>

        <link name='chassis'>
                <pose>0 0 0.1 0 0 0</pose>
                <collision name='collision'>
                        <geometry>
                                <box>
                                        <size>.4 .2 .1</size>
                                </box>
                        </geometry>
                </collision>

        <visual name='visual'>
                <geometry>
                        <box>
                                <size>.4 .2 .1</size>
                        </box>
                </geometry>
        </visual>

        <collision name='caster_collision'>
                <pose>-0.15 0 -0.05 0 0 0</pose>
                <geometry>
                        <sphere>
                                <radius>0.5</radius>
                        </sphere>
                </geometry>

        <surface>
                <friction>
                        <ode>
                                <mu>0</mu>
                                <mu2>0</mu2>
                                <slip1>1.0</slip1>
                                <slip2>1.0</slip2>
                        </ode>
                </friction
        </surface>
        </collision>

        <visual name='caster_visual'>
                <pose>-0.15 0 -0.05 0 0 0</pose>
                <geometry>
                        <sphere>
                                <radius>0.05</radius>
                        </sphere>
                </geometry>
        </visual>

        </link>

        <link name='left_wheel'>
                <pose>0.1 0.13 0.1 0 1.5707 1.5707</pose>
                <collision name='collision'>
                        <geometry>
                                <cylinder>
                                        <radius>0.1</radius>
                                        <length>0.05</length>
                                </cylinder>
                        </geometry>
                </collision>

                <visual name='visual'>
                        <geometry>
                                <cylinder>
                                        <radius>.1</radius>
                                        <length>0.05</length>
                                </cylinder>
                        </geometry>
                </visual>
                </link>

        <link name='right_wheel'>
                <pose>0.1 -0.13 0.1 0 1.5707 1.5707</pose>
                <collision name='collision'>
                        <geometry>
                                <cylinder>
                                        <radius>0.1</radius>
                                        <length>0.05</length>
                                </cylinder>
                        </geometry>
                </collision>

                <visual name='visual'>
                        <geometry>
                                <cylinder>
                                        <radius>.1</radius>
                                        <length>0.05</length>
                                </cylinder>
                        </geometry>
                </visual>
        </link>


        <joint type='revolute' name='left_wheel_hinge'>
                <pose>0 0 -0.03 0 0 0</pose>
                <child>left_wheel</child>
                <parent>chassis</parent>
                <axis>
                        <xyz> 0 1 0</xyz
                </axis>
        </joint>

        <joint type='revolute' name='right_wheel_hinge'>
                <pose>0 0 0.03 0 0 0</pose>
                <child>right_wheel</child>
                <parent>chassis</parent>
                <axis>
                        <xyz> 0 1 0</xyz
                </axis>
        </joint>



        </model>
<sdf>