I know this discussion was a few months ago but wondered if anything came of it by way of solution. I have the same problem with 2020. It does not matter if the "allow multiple instances of band-in-a- box to be running" box in preferences is ticked or not it always opens another instance of BB when a song is clicked in Explorer. This did not happen in 2019. I have reinstalled it again plus the latest upgrade but to no avail.