Welcome to the jupyter-vcdat wiki!
The VCDAT development team created VCDAT 2.0 as a JupyterLab extension so it makes use of all the generic features available via the JupyterLab interface, but adds additional functionality needed to perform CDAT functions like selecting a subset of data from a netCDF file and plotting that subset of data.
The JupyterLab file browser allows you to double click on a file to open it. Unfortunately this means loading the whole file into the browser. For netCDF files this is not practical (these files can be several Gb), so we kill the transfer to prevent the file from loading. Unfortunately this brings up the following error message. You can safely ignore the error message and move on. The creators of JupyterLab are aware of the problem and are implementing a solution for big files.