Unable to load msg [sensor_msgs/]

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when I use the instruction rosmsg show sensor_msgs/ I get the following weird error:

Unable to load msg [sensor_msgs/]: Cannot locate message [] in package [sensor_msgs] with paths [['/opt/ros/noetic/share/sensor_msgs/msg']]

but when I type ls /opt/ros/noetic/share/sensor_msgs/msg I get the following output:

BatteryState.msg     Illuminance.msg       JoyFeedback.msg    MultiDOFJointState.msg  PointCloud.msg        Temperature.msg
CameraInfo.msg       Image.msg             Joy.msg            MultiEchoLaserScan.msg  PointField.msg        TimeReference.msg
ChannelFloat32.msg   Imu.msg               LaserEcho.msg      NavSatFix.msg           Range.msg
CompressedImage.msg  JointState.msg        LaserScan.msg      NavSatStatus.msg        RegionOfInterest.msg
FluidPressure.msg    JoyFeedbackArray.msg  MagneticField.msg  PointCloud2.msg         RelativeHumidity.msg

can you please tell me what is my mistake? thanks in advance.