What ultimately worked for me was the following:
Headset powered on, not plugged in.
Insert dongle.
Wait.
Settings -> Device -> Update firmware
Ensure Force Firmware is checked.
Update.
At 97% of the top bar, the headset turned off and seemed to be making no apparent progress. Turned the headset back on (short hold).
Update should continue. Let update finish.
Update should be finished. Turn off headset if it is not already off at the completion of the update.
Press and hold headset power button until green and red lights at the end of the microphone rapidly flash.
While continuing to hold, use a paperclip or sim removal tool to press *AND HOLD* the reset button on the dongle located roughly halfway between the indicator light and the USB port it is plugged into.
After a few seconds everything finally worked.
