The connection to the server controlplane:6443 was refused - did you specify the right host or port?

Kubernetes
#1

Hi, i am unable to access controlplane node a as a part of " Lab- Kubernetes Challenge 2".
I am getting below error
The connection to the server controlplane:6443 was refused - did you specify the right host or port?

can you please any one suggest me how can we enable port 6443?

#2

If you have not done CKA you will not know how to fix the controlplane or node01

Take the solutions for those two only from here.