I see in your original comment that you’re trying to program recent firmware, v0.11.1. That version is incompatible with what your bridge is currently running, which is reported as v0.4.0 in the gist.
As of v0.11.0 there was a breaking change with any versions before. You can learn more about that in the release notes.
In order to put v0.11.1 on your dev kit and have it work, you’ll first need to update your bridge. Once that’s successfully updated, you’ll need to update your Spotter firmware.
The clearest instructions I can offer for that are in the CircuitPython guide — just follow steps one and two to update the Bridge and Spotter, and then ignore the rest.