Thanks for the note @ftheile and @xerxesb. You’re both correct, I used the “8-bit address” instead of the correct 7-bit address (see more on the two here: https://www.totalphase.com/support/articles/200349176-7-bit-8-bit-and-10-bit-I2C-Slave-Addressing).
I’ve fixed the post to refer to the 7-bit address: 0x66.
Thanks again!