When web service(jupyter lab) can not start, please check the following points.

check the log and investigate what is happening

Output files of web services are saved under ~/.t3was/.
There might be some hints in the files.

Initialize the environment

Initialize python 3.6 environment such as moving ~/.local/lib/python3.6/ to another directory, and then do

$ python3 -m pip install --user (modulename)

module conflict might be solved.

if web service was able to start by doing this, install some necessary modules from the jupyter lab console, and then

$ python3 -m pip check

this checks the dependencies and update problematic modules by doing

$ python3 -m pip install -U --user (modulename)

, the problem can be solved.

Check and resolve module dependencies, avoiding initialization of the environment

This is almost the same as the abobe, after SSH'ing to TSUBAME, do

$ module load jupyterlab/3.0.9

then the environment of Jupyter Lab in the web service is loaded.(3.0.9 is necessary)

After this, execute

$ python3 -m pip check

and check if there is problematic modules in  the dependencies.

If there is, do

$ python3 -m pip install -U --user (modulename)

and update them.