Timed out waiting for packet header esptool.FatalError: Failed to connect to ESP8266:

trying to load the MQTT sample sketch from the below tutorial.  
https://randomnerdtutorials.com/esp8266-and-node-red-with-mqtt/
the sketch compiles, but upon upload I get the following error:
Timed out waiting for packet header esptool.FatalError: Failed to connect to ESP8266:
I’m using:
A  Windows 10 machine, running Arduino IDE 1.8.8
Trying to load it to A nodemcu 0.9.
Thanks in advance to anyone who can assist!