Hi Tor,
The example code I was referring to came with PPS but I've never run it as I don't use PPS to connect to the chip directly (only really useful if your using the dev board). I have never looked at register 108 to be honest but it might be indicative of some hardware issue such as zero data detect as described on page 63 of the datasheet.
If you are just getting started and want to test your hardware set-up is ok I have found that you don't need to communicate on I2C / SPI at all just to get an output signal from the chip. In my experience if you have followed the application circuit, have a valid I2S input and XSMT pin25 is pulled high it will make some sound. I've had three of these chips on the same bus using a DRI9001 as the I2S master all hand wired on a breadboard working well so they must be fairly robust.
Let me know how you get on,
Andrew.