Unable to register with master node in Python 3 for Robotics Course

Hi. We are going through the Python 3 for Robotics Course, and one of our students got the following error in the terminal when trying to run his program: Unable to register with master node [http://1_simulation:11311]: master may not be running yet. Will keep trying."

Could you please help? Thank you.

Daniel, tell the student to write the question himself here and include all the details about it. We cannot solve the problem just saying I have this problem. We need to know all the details in order to solve the problem