I started an iphone-based update of the firmware on my bose QC35ii headphones today. I don't remember the exact firmware version that I had on the headphones before attempting the update but it was definitely 1 major version number lower than the current. I started by updating the iOS bose connect app on my iphone to the latest version (3.1.0), at which point I connected my headphones to the app, an update was suggested and I began downloading the firmware. After that process, I tapped the "update" button on my iphone and the firmware update began. A few minutes later, I received an error saying that the update was taking longer than expected and it had failed. At this point I was unable to turn on the headphones, when I plug them in, no lights turn on to indicate a charging state, and I cannot connect them to my PC to initiate a manual update from the PC either.
Currently, the headphones are completetly non-operational and it doesn't seem there is any way to force an update of the firmware to get them back to a working state. Please help!