The way to check the CRC status is to read a register in the VBUS memory area. I think that your code to read the VBUS memory area is not working correctly hence is always returning 0.
If you get a value of 0 for all VBUS registers then there is something wrong reading VBUS registers. Try writing to one of the VBI registers then read it back to make sure reading is working.
Check section 2.6.3 in the datasheet for more information.
BR,
Steve
