pr2 joint state not publishing

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Hi everyone, I'm pretty new to ROS and I am trying to follow the tutorial on using the pr2 model with gazebo: http://wiki.ros.org/pr2_simulator/Tut...

When I fire up the simulator and try to print the joint_states for pr2 I get the following error

~ $ rostopic echo /joint_states WARNING: no messages received and simulated time is active. Is /clock being published?

I checked /clock and it is being published with no issues.

Am I missing some step to get the joint_state messages?

I am running ros indigo on linux mint

Thanks!