Well, there's a section in the H9 Control manual that deals with connectivity problems. Could you please read through the section on connecting on Windows to an H9 via USB?
One thing the manual doesn't mention which can sometimes also help is just restarting the computer… And another option would be to get a Bluetooth dongle and connect over Bluetooth instead, although it can be tricky on Windows to find a Bluetooth dongle that works. This thread has some advice on that:
