I finally managed to fix this issue.
It turned out this one was caused by absence of gripper controller in “ros_controllers.yaml” in “config” directory in “fetch_moveit_config” package.
I couldn’t find out a way to add controllers for gripper that has “GripperCommand” type, so I manually changed the context in “ros_controllers.yaml”
After the change, I was also encountering another issue with gripper’s behavior that width of its fingers became too narrow right before it attempted to grasp the detected object(i.e., a cube)
Therefore, I had to investigate and change the code in order to prevent this behavior.
I modified a line of code in “shape_grasp_planner.cpp” in “simple_grasping” package.
Then, the issue had been resolved and the Fetch robot successfully performed the pick and place task.
Hope it will help someone will meet the same issues as I did.