[DOC] - Panel apps occasionally no longer visible in JupyterLab

Preliminary Checks

• This issue is not a question, feature request, RFC, or anything other than a bug report. Please post those things in GitHub Discussions: https://github.com/nebari-dev/nebari/discussions

Summary

I've had a situation happen a few times where I was working with Panel one day and I come back the next day and the app will no longer display in a jupyter notebook. This happens with no changes to the notebook, or the environment.

Looking in the java console, at the beginning of the traceback there is a statement Bokeh: BokehJS was loaded multiple times but one version failed to initialize. Then, every time you try to visualize a panel object the java console shows ERROR: Unable to run Panel code because Bokeh or Panel library is missing.

I've spent loads of time trying to figure out how it got in this state and I've gotten nowhere. The workaround I've been using for a while is to shut down my server, and open an incognito window and restart the server there. So I'm fairly certain this is a caching issue of some sort.

Today I discovered a better solution - if you shutdown ALL your open kernels, restart and clear all in the notebook, save the notebook, then REFRESH the whole browser page... it will start working again. Note - if you simple restart and clear all on just one notebook, it will not fix it.

I'm not sure why this is happening, but I've had to deal with this enough times and have spent enough time being baffled, that I think its worth an FAQ mention on how to fix.

Steps to Resolve this Issue

1. Shutdown all kernels
2. Restart and clear all in the notebook of interest ()
3. Save the notebook
4. Refresh the browser.

If this happens again, I'd first want to check if a browser refresh alone would work, then I'd add these other steps in one by one. Since I can't reproduce the error, I'm not sure what is the minimal required.

Start with the issue's reported recovery steps: shut down all kernels, restart and clear the notebook, save it, and refresh the browser. Check whether a refresh alone is sufficient, then identify the minimum reliable sequence before documenting it as an FAQ. Done means the troubleshooting guidance clearly explains how to restore Panel apps in JupyterLab.