We have a load of new WD19 docks. They work perfectly with Dell Laptops, by which I mean you can have two monitors connected to the dock, and then the additional laptop screen (three in total). The MacBook Pro doesn't work. I get one extra screen, but not the second. I have used a D6000 dock in the past, and that worked fine. Any help would be appreciated.

Andy

P.S. the laptop charges fine as you would expect.