Duo v1 expansion: 2x 750GB to 2x 2TB - But Volume Not Larger

Ok, it was about an hour and it wasn't showing any change so I tried to turn the NAS of via the power button - nothing happened - so I took a risk and just unplugged it from the mains. Then tried the procedure again, hold reset button in, push power button, and wait for the led flashes. But the same thing happend - after 5 seconds both disk leds flash once, then about 10/15 seconds later they do it again just once, and then another while later the 2nd disk led is lit and the power button is remains blinking fast and the NAS does nothing. Got no idea why I'm not getting the proper boot menu led flashes while depressing the reset switch in on power on - all a bit odd.