When executing the gazebo startup file it appears:

[ERROR] [1632398141.557684, 290.045000]: Spawn service failed. Exiting.

[urdf_spawner-6] process has died [pid 5510, exit code 1, cmd /opt/ros/noetic/lib/gazebo_ros/spawn_model -urdf -model mrobot -param robot_description __name:=urdf_spawner __log:=/home/wyf/.ros/log/28660358-1c66-11ec-aa75-efd91e7f34ce/urdf_spawner-6.log].
log file: /home/wyf/.ros/log/28660358-1c66-11ec-aa75-efd91e7f34ce/urdf_spawner-6*.log

Solution:

source ~/catkin_ws/devel/setup.bash

Execute the launch file again

Another problem is that the model file is not added