Just my 2cents worth here for people flashing using Windows as a "host" for the VM
Firstly, "flashing" a device is never "fun" and the VM method that they have devised, despite the issues some are having, is a lost LESS trouble than I would expect
These are my unscientific observations, and advice.
1) when the CHIP is is plugged in in FEL mode, it doesn't matter if Windoze has a driver or not! As long as it "bongs" to say that SOMETHING was plugged in! I personally would stop Windows looking for any driver.
2) when you plug it in and the Flashing VM is running, you should see stuff on the black screen... Unless it says it failed, do NOTHING, but wait! When I flashed mine it took quite a while, a good 5 minutes
3) When the Flashing is finished from the VM the VM MAY error (looking for a CHIP in FEL mode) after the CHIP reboots, Windows will whinge & carry on, as the USB device changes state and bing & bong etc. again DO NOTHING ... Simply wait until the light on CHIP starts to flash.
4) When the light flashes disconnect CHIP, the and take the FEL header off ( paperclip)
So my advice, is to "do nothing" unless you are 10000% sure it has failed. Mine took a good 10 Minutes all up (maybe not that long but it felt like it LOL!).
If it fails , try again! That is the rule of Flashing ( thank goodness it is not going to "brick" the device if it fails!!!!)
If all that fails, try another PC