Mash attractor object not attracting
 

I'm using Maya 2020 and Mash Flight node to animate a school of fish. As in this tutorial by Ian Waters
I've middlemouse dragged a locator to Attractor Objects on the flight node and messed with the distance and strength, but the fish aren't following the locator at all. When I dragged the locator onto 'Attractor Objects' in the attribute editor, Maya shows the locator as 'UnitConversion'. Could that be something to do with why it's not working?
Any help welcome thanks.