add extensions 500 Internal Server Error

[joequant]

Error communicating with server extension. Consult the documentation for how to ensure that it is enabled.
Reason given:

Error: 500 (Internal Server Error)

[joequant]

Here is the problem

https://discourse.jupyter.org/t/jupyterlab-extension-manager-on-jupyterhub-for-individual-users/4467/10