Billy and I attempted to solve our problem today by soldering the Adafruit Hat to the included 2×20 pin header. Once soldered and oriented properly, the device appeared to short out. This is behavior that I was seeing when trying to connect the hat without soldering and making physical contact.
After some software troubleshooting, and some assistance from Phoenix and Matt, we came to the conclusion that the Adafruit hat was either damaged during installation or DOA. I’ve ordered a replacement that we can try to work with next week. Until then, the code appears to be sound.