Rviz not subscribing to visualization_marker? [closed]

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I am trying to add points to rviz following the tutorial "Markers: Points and Lines". Even when I followed the code and instructions exactly like in the tutorial, I could not see the markers displayed in rviz. $rostopic echo visualization_marker showed that the topic was published well and continuously. When I tried $rostopic info visualization_marker, I realized that there was no subscriber to the topic. How come rviz was not subscribing to the topic? Any idea what is wrong?

Thanks! :)