One of the likely causes of not being able to connect to a Jupyter session is that you have run out of space in your $HOME and the jupyter notebook session cannot start as some connection files cannot be written.
To check your quota, please connect with a terminal and SSH and issue:
myquota
to see what is taking up space in your $HOME directory, please connect with a terminal and SSH and issue:
find ./ -maxdepth 1 | xargs -i du -sh {} | sort -rh
the command will take a few minutes to run but it will give you a
summary of what is taking up space so that you can decide what to move
or remove.