unable to visulize PointCloud using octomap_mapping

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I am using Turtlebot3 Burger in gazebo simulation. Since it does not have pointcloud2 data, I use laser_geometry package to convert the scan data into pointcloud2. I want to use the octomap_mapping in octomap_server to visualize the pointcloud data. Based on some instructions, I modified the octomap_mapping.launch: <remap from="cloud_in" to="pc"/> where "pc" is the pointcloud2 converted by laser_geometry.

But when I open rviz and use MarkerArray to visualize the occupied cell, it does show anything. I tried to look at the message in the /occupied_cells_vis_array, and It says no message warning.

Could anyone help me figure out what is going wrong? I am really new to ROS, thanks for patience.