Hello! Perhaps this can help someone else avoid a bit of frustration.
I struggled with applying the update using my iPhone. After swapping out cables, adapters, testing the lightning to 1/8 in. adapter, etc., I finally realized that Settings > Sounds & Haptics > Headphone Safety > “Reduce Loud Sounds” needed to be turned off.
It appears that the send volume was not loud enough with this setting enabled and the symptom that I was experiencing when the update wasn’t working was: LED lights would glow / pulse, ready to receive data, but wouldn’t change status after 6 seconds.