I just bought a (genuine) Arduino Nano 33 BLE, installed the latest version of Arduino IDE on my MacBookPro (2009) running Mac os X 10.11 El Capitan.
From the IDE I can see the Arduino Nano Board, and from ports I select /dev/cu.usbmodem411.
Few seconds after running "Upload" my Mac shutdown.
In the past I programmed without problems an Arduino Mega on the same laptop.
Thanks a lot,