Rekordbox database won't move

I've done this before, so I know it should work - but it isn't.

Followed this video https://www.youtube.com/watch?v=hNbZEqRo_tU but when I opened Rekordbox on my new mac, clicked on my external Lacie hardrive where I had moved the database - Rekordbox wouldn't update. Still blank.

Now both my Rekordbox databases are completely blank! :(

The database must live on the external Lacie hardrive somewhere as I moved it there. What do I do???