Need help to debug Invalid response: 404 not found error

[KevinRyu]

Hello,

I'm trying to debug "404 not found" error. Because I have no experience about front-end and back-end development, I manage to trace java source code for this extension. And I can't find the location of error log files.
I have doubt the initial 'logdir' default path but.. I don't know.. Can anyone give some advice for me? And how can I find back-end code or error log?

Error message in my terminal:

[W 2021-07-12 21:56:07.392 ServerApp] 404 GET /api/tensorboard?1626094306420 (127.0.0.1) 1.42ms referer=http://localhost:8888/lab

Screen capture of debug in chrome browser:

[KevinRyu]

Hi, I succeeded installation and operation in jupyterlab 3.0.15 (No errors)
I just followed tips from Mr. k-markov.

This is installation order what I tried.

1. pip Installation jupyterlab & tensorflow
   Jupyterlab 3.0.15
   tensorflow-gpu 2.5

2. Installation tensorboard
   pip install git+https://github.com/cliffwoolley/jupyter_tensorboard.git
   pip install git+https://github.com/chaoleili/jupyterlab_tensorboard.git

That's all.