CrossFire Pro not recognized

Hey guys!
We just picked up a Crossfire Pro and are excited to use it. However, we cannot get it to be recognized by our computers at all. We tried two different computers, we used a different USB cable that we know works. We also checked for the table in the device manager where it just won’t show. After uninstalling and reinstalling all USB drivers… still nothing. One of the computers runs Windows 7, the other one Windows 10.
The motors start buzzing when the control box is turned on and the green LED lights up when the USB cable gets plugged in. Finally we confirmed that all electronic components are properly seated.
I don’t know what else to do. Any suggestions, fellers?

is the green LED lit on the mainboard? you don’t need to power up the control box as the main board gets power from the usb cable.

Yes, that one lights up, too.