Voice isolator not working?

I downloaded audacity so I could isolate vocals from a song but for some reason the plugin only lets me use the mono options, which are to remove vocals or remove center. every other option simply does not work: pressing the preview button does nothing, and pressing the OK button just closes the plugin window without actually doing anything. help please?

That’s a bug. It has been fixed for the next Audacity version (3.0.1) which we hope to release next month.

In the meantime, the previous version (Audacity 2.4.2) is still available from here: https://www.fosshub.com/Audacity-old.html