Unable to connect

I installed the kernel on the raspberry. While the goatchurchprime kernel is working without issues, this one fails to connect with this error:

Could not connect to localhost: 9876
Traceback (most recent call last):
  File "/home/pi/.pyenv/versions/3.6.6/lib/python3.6/site-packages/_pydevd_bundle/pydevd_comm.py", line 442, in start_client
    s.connect((host, port))
ConnectionRefusedError: [Errno 111] Connection refused

I'm using Jupyter Lab with kernel modified to use the local python 3.6.6. Jupyter is working with Python 3.6 kernel and also with goatchurchprime micropython kernel.