From this page I see that convertor comes bundled with Magix Video Easy SE, rather than the VE HD 4 which you say you have, but have you followed the procedure given in that manual to install the software? I suspect you may need to first install the included software in order to ensure the necessary drivers are in place.
With the unit connected to your PC, if you go into Device Manager is the converter listed and shown as working?
If not and you are using Windows 10 or 11 check the Program Settings, Privacy & Security, Camera and Microphone options have the Let desktop apps access your Camera/Microphone turned on.
If the device can be selected then, if recording from a VHS player, ensure that the SCART connector is switched to Out, if it has a In/Out switch on it, and it is plugged into a SCART out on the player, if it has 2 or more SCART sockets, and the Composite input is selected in Video Easy.