require `debug/dissect`: nonexistent file or invalid filename

Using J9.6 (Qt) on Windows. I installed 'debug/dissect' via the GUI package manager. It is shown as installed at "4.6.49", but a `require 'debug/dissect'` leads to: "nonexistent file or invalid filename", but "...\appdata\local\programs\j9.6\addons\debug\dissect\dissect.ijs" does exist.