[Bug] /laser_scan topic shows no data

Hi everyone,
I’m trying to do Section 3.3 and look at the laser scan data. But whenever I echo the topic nothing appears in the Terminal.

If I look up the topic info, everything seems fine:
user:~/ros2_ws$ ros2 topic info /laser_scan
Type: sensor_msgs/msg/LaserScan
Publisher count: 1
Subscription count: 0