after starting the Bose-USB-link-Updater and updating the firmware to 0074, I was asked to restart the device by unplugging and plugin it in again. After doing so the Device doesn't seem to connect and all lights are off. Could you upload the previous firmware? I noticed the software is able to flash it.
1. I don't work for Bose but they will not be able to help you unless you say exactly which Bose product you had and exactly what you did - what you started with and what you ended up with and then what was the result.
2. Bose has a corporate policy for all it's Bluetooth products that you can only upgrade to the current version. There is no way to go back.