Which version do you have? The ASI1200MM (USB2) or the ASI120MM-S (USB3)? The first one doesn't work on modern operating systems due to a faulty camera firmware that doesn't implement the USB2 protocol properly (too large packet size). Some people have had luck getting it to work though by flashing it with the so called non-compatibility firmware. Search on Google and you should be able to find how to do it. The ASI120MM-S works flawlessly.
