[Errno 121] Remote I/O error

Getting an error when trying to import rainbowhat on Pi Zero W. Things are working with my Raspberry Pi 3.

>>> import rainbowhat as rh

Traceback (most recent call last):
File “”, line 1, in
File “/usr/lib/python2.7/dist-packages/rainbowhat/init.py”, line 13, in
File “/usr/lib/python2.7/dist-packages/rainbowhat/HT16K33.py”, line 52, in begin
self._device.write_i2c_block_data(self._i2c_addr, HT16K33_SYSTEM_SETUP | HT16K33_OSCILLATOR, [])
IOError: [Errno 121] Remote I/O error

BTW, this is a Pi Zero W