It works for me when I use this URL: https://localhost:9999/?name=head-mr.vti&url=https://kitware.github.io/vtk-js-datasets/data/vti/head-binary-zlib.vti
I load it, save state, then I can load the resulting glance file and the dataset shows up. Can you provide more details as to what is the error you get now, if it’s different from before?