Make sure that your device is connected to your computer directly and not through a hub.
Use the rear USB ports of your computer, not the front USB ports.
Disconnect all other USB devices from your computer which aren’t needed at the moment.
Change the USB cable or try from a different computer.
On Mac: Click on About this Mac in the Apple menu. Select System Report. Go to the Hardware dropdown menu on the left and unfold it. Select USB. Check if your device is listed there.
On Windows: Press the Win key+R. Enter devmgmt.msc and press OK. Check if your device is listed there. If it shows up as an “Unknown Device” and if there’s a black and yellow warning sign, deinstall the driver. Then unplug the instrument, reboot your machine and plug it back in.