C0040401 error: no connection with controller

Sorry, guys, I am new to ABB robotstudio.
I want to use ABB IRB140 for welding. Currently I try to study RAPID programming.
I have input all my models, including robot, tool and work piece, and then planned a short path, in the simulate module I synchronized the path to the VC already, then I can simulate the robot path, no problem.
And now, I want to test the RAPID programming. In the controller and RAPID module, I can see the generated RAPID code, and then if I want to change the RAPID code, and start execution of the RAPID code, there is C0040401 error: no connection with controller. However, even if I do not change any RAPID code, the same error.

How to fix this problem? Is there any examples to start RAPID programming?

Thanks
Best regards

No answer? Nobody has this problem?

No reply? Nobody has this problem?