I am pretty new and have installed the above referenced HAT. I followed the instructions, but it is not detected.
I have power and a green LED on the board and when I turn it on and off the servos jump a bit, so it seems like it is physically OK. I have enabled I2C, but it doesn't show up.
I am using RPi 3 B+ with the latest Raspbian install. I am pretty new, so let me know what other info I need to provide here. I see this is a common topic and it usually seems to be a power issue, but I am pretty sure that is not my issue.