First an explanation of USB 2 vs USB 3...
USB started with a 4-wire connector, a 5V power, a ground return, and a differential data pair. It is half duplex (i.e., cannot transmit and receive at the same time; it multiplexes the input and output data on that single pair of differential data pair).
In addition to the 4 pins of USB 2, USB 3 added 5 more wires. It uses the same power and ground, and adds two extra sets of differential data lines (one pair for high speed output and one pair for high speed input data). The fifth wire is the ground drain (to ground the shields that USB 3 cables are supposed to include).
USB 3 uses the original 5V and ground wires for power, and keeps the original differential pair to maintain backward compatibility with USB 2.
On a USB 3 Type B connector, the extra 5 pins are in that hump in the connector. On a USB 3 Type A connector, you can see the original 4 pins, and if you look deeper into the connector with a flashlight, you can see those additional 5 pins.
When modern software detects those extra two pairs of data lines, it will use USB 3 protocol. Otherwise it will revert back to use USB 2 protocol on the original 4 pins.
If you have a Mac, first plug in the camera, then open the Apple Menu from the Finder(Apple icon on the left of the main menu bar) and select "About this Mac." This opens the System Information window.
On the left panel of System Information, select Hardware > USB.
The USB Device Tree will show up on the right. Then look for the camera in USB Device Tree on the right side. Your camera should applear with the ASI1600MC name. Click once on that name.
The bottom right of the System Information, you should see see details of the camera's USB port.
Specifically, look at the Speed of the camera. If the Mac cannot see those extra 5 pins of a USB 3 device, but can see the original 4 pins, it will say "Up to 480 Mb/s."
If the camera has a functioning USB 3 port, it should say "Up to 5 Gb/s." ZWO's cameras do not support USB 3.1, otherwise Speed can also show up as "Up to 10 Gb/s."
If you do not see "Up to 5 Gb/s," the computer cannot see the USB 3 pins. So, either (A) the cable is defective, or (B) the extra USB 3 pins on the camera is not responding to the USB 3 protocol.
Be sure never to use the flat USB cables that ZWO includes in their boxes. It is not shielded (and will accept and also put out interference to other devices, especially with WiFi and BlueTooth). Use a real shielded USB 3 cable (Amazon has plenty, and unless they are longer than 1 meter, I have not yet found even cheap cables at Amazon to not work. (Beware the longer cables.) Again, do not use any USB cable that comes in the ZWO boxes.
If a good cable still fails, I would contact the dealer you bought the camera from, so they can help you get it repaired (they will also probably test it too before repairing).
Remember, if your computer can see the camera on USB 2, it simply means that the slower 4-wire interface is good. If the computer cannot also see the device at the end of those extra 5 wires, it will not report that the camera is capable of USB 3 speed and protocol. USB 2 and USB 3 data run off completely different sets of wires in the cable.
Chen