I2C communication problem with nRF52840
It seems quite likely this is a firmware issue on your nRF chip, especially since you were able to get good readings from Arduino example code. 

Try messing with the original nRF example code until you get some activity on your scope. Check basic settings first, like pin mappings and whether the right I2C peripheral is getting enabled. Once you've gotten that, implement your interface to your sensor in small steps, verifying them as you go. A good first step is to read the 'WHOAMI' register of the LSM6DSR.