There are two common issues with upgrading 2.1:
1. If the button is pressed too long, Windows will think the device has lost response. So make sure the button is released within 1-2 seconds after the USB cable is plugged in (this has been mentioned in the instructions).
2. If you click on ‘Auto Detect’, the controller will exist the bootloading mode, so before clicking on ‘Upload Firmware’ please enter bootloading mode again. In fact, if you already know you have OS 2.1, you can directly select it from the dropdown list, and there is no need to do ‘Auto Detect’. Auto detect is only there for users who don’t remember which hardware version they have.
Hope this helps.