I strongly suggest to deinstall the catalyst driver and reinstall the driver first by using a single display.
Once the driver is installed, turn off the system, power off the system and drain the power by pressing the on button on your pc (make sure that the power supply is disconnected from the power cable.
Place everything back again, connect the mst hub to your displayport output, the 3 displays and power on the system. You probably will see all screens on or just a single display. Proceed to configure your display arrangement.