PMW3901 on Raspberry Pi

Has anyone got a PMW3901 (https://www.tindie.com/products/onehorse/pmw3901-optical-flow-sensor/) to work with a Raspberry Pi? I am using it with the Pimoroni library (https://github.com/pimoroni/pmw3901-python) with wiring:

SCK → SCLK (GPIO11 / PIN 23)
GND → GND
VIN → 3V3
SO → MISO (GPIO9 / PIN 21)
SI → MOSI (GPIO10 / PIN 19)
CS → CE1 (GPIO7 / PIN 26)

SPI enabled on the Pi
Trying to run https://github.com/pimoroni/pmw3901-python/blob/master/examples/motion.py

and triggering the RUntime Error on Line 53 of https://github.com/pimoroni/pmw3901-python/blob/master/library/pmw3901/init.py

So, it’s basically not reading the ChipID and unable to proceed. Any advice welcome. Thanks.