Jupyter_scheduler extension : Unhandled error


I installed jupyter_scheduler following https://jupyter-scheduler.readthedocs.io/en/latest/users/index.html#installation.

After installation and checking that both the server extension and the lab extension are enabled, I face this error:

When opening " Notebook Jobs" from the JupyterLab launcher, a message “Unhandled error” is displayed.

As well, when I try to schedule directly a notebook, I am not able to create the job. In the “Create Job” dialog, it keeps displaying " Loading …".

Is there any way to see what this error points to so I can try to figure out why the jupyter_scheduler extension does not work on my JupterHub server?

Thank you