Hi Roy, One thing that's potentially a bit unintuitive and has caught me out a couple of times is that if you click the "choose directory" button on the "select import files" dialog, it is looking for a folder (i.e the one with the zip'd JSONLD file in it), not the zip file itself.
Once you've selected the folder containing the zip file, it should be an option in the box on the right hand side of that dialog.
Possibly this isn't the problem you're seeing - apologies if so as your description is a bit different - but hopefully it helps. Sam