I was getting an error when trying to install the filter driver through Zadig. The way to get around this issue is to download libusb-win32 from libusb-win32 download | SourceForge.net and use the filter driver installation included with files.
The “backend” error indicates that the libUSB driver is not installed. So you need to install the driver either using the directions on the K40 Whisperer web page or you can use the installer linked here. I would recommend using the directions linked on the K40 Whisperer web page unless you know what you are doing.
I will try that tonight when I get home, is it normal for it to work correctly with drwlaser just not with K40 whisperer? I engraved and cut it out the other day but I made the file in drwlaser and used it to engrave and cut.
@Frank_Jones LaserDRW uses a different driver. So you need to install the libUSB driver for K40 Whisperer to work. There is some discussion about that in the instructions I linked.