How to connect URSim with ROS?

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I want to manipulate UR5e with ROS.

I manipulated UR by sending topic which is named "/joint_group_vel_controler/command" to URSim node successfully. Successfully means that I could control robot pose as I wish by sending each joint velocity.

But after rebooting ,it doesn't work well.

As well as it work successfully, same topic is sent to same node.And maybe the setting on URSim is not changed.

I can't understand what cause this problem. Please help me.

what I want to ask is below.

1. what are dependencies,setting on URSim to note?
2. In the first place, when you want to control UR by joint velocity, which topic do you send to URSim ? "/joint_group_vel_controler/command" is correct?