No response from ST LSM6DS3 IMU breakout board using SPI
[Since this was confirmed as the solution from my comment, here it is as an answer:]

The SparkFun LSM6DS3 breakout allows either the device's SPI or I2C interface to be used. However, the breakout PCB is supplied by default with a soldered jumper in-place, labelled "ADDR", which selects the I2C address from a choice of two. However that soldered jumper prevents SPI communication on the MISO connection, and must be removed if the breakout module is used with the SPI interface.

This requirement is briefly mentioned in the SparkFun LSM6DS3 Breakout Hookup Guide: