Attaching any block device via sys-usb most likely won’t work, and that is why it is strongly suggested to attach it as a block device. To know if you properly installed QWT just try to attach some non-block device - some usb wifi adapter or similar and try to attach it to win qube. It should work.
All of these could be read on the forum, for example here
Did you for example installed these drivers after QWT?
https://www.dell.com/support/home/en-yu/drivers/driversdetails?driverid=x2nf0
Summary
Not to say we still don’t know which Windows you are using.