Vehicle moves in RVIZ but not in Gazebo? Using ros_control with the four_wheel_steering_controller

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Hello!

I am trying to use the four_wheel_steering_controller from the ros_controllers package (which leverages the ros_control package).

Specifically I'm trying to launch this launch file: https://github.com/ros-controls/ros_c...

When I first launched it, I noticed that many of the joints in the model collapsed. After making sure inertia tags were correct, I added mass to small inertia links.

Now I can see the model in gazebo properly, but it still doesn't move. It DOES move in RVIZ when given controller input when I use odom for the fixed frame. I can drive it around like normal in RVIZ, but nothing changes in Gazebo.

I've made some changes to the code which I've committed to my own branch here: https://github.com/tlalexander/ros_co...

One thing I had to do was add PID gains to a yaml file: https://github.com/tlalexander/ros_co...

Ultimately though I still can't get it working. I'm really at a loss for how to begin debugging this after spending all day on it.

Can anyone direct me for how to determine why the Gazebo model doesn't drive? Are the wheels not being commanded to rotate properly? Am I missing gazebo tags in my URDF? Are my PID values being specified properly?

Other details:
OS: Debian Buster
ROS Version: Not sure? The debian repos don't include the ROS version in their name so I'm not sure how to tell.

Thank you!