Exercise 2.1b no LaserScan why

When running exercise 2.1b, when running rviz2 (after the source command) nothing shows up in the window relating to LaserScan. But when i open my rviz , the status was error and i cant find the map or robots

Hello @yusufbadriawan ,

Make sure that the configuration of the display is the proper one as shown in the notebook: