Is your board “XIAO_nRF52” instead of “XIAO_nRF52_Sense”?
I ran the IMU sketch on “XIAO_nRF52” and got the same results as you posted.
Try running the attached I2C scanner sketch, can you find the IMU address “0x6A”?
nRF52_XIAO_mbed_I2C1_scanner.zip (809 Bytes)