I bought the Zumo 32U4 a while ago. It did already work in the past with Windows 7. Now after a while I tried to install the driver (a-star-2.0.0) in Windows 10 Version 1703. Windows replied everything okay but the driver doesn’t appear in the device manager of Windows and the port isn’t shown in the Arduino IDE.
Can you try using a different USB cable (one that you know is working) if you have not already done so? Some USB cables (e.g. cell phone charging cables) are power-only cables and do not have the data lines.
If changing the USB cable does not fix the issue, can you select the “Device by connection” option under the “View” menu in the Device Manager, expand all of the “USB host controller” entries, and post a screenshot of it here?
Oh my god. I can’t believe it. I didn’t know about these differences and really used the cable from my new power bank that was lying around. Excuse me for wasting your time.