Upload fails: "ser_open(): can't open device "/dev/cu.usbmodem11201": No such file or directory"

Development Tools Uploading
1

Arduino: 1.8.16 (Mac OS X), Board: "Arduino Uno"

Sketch uses 924 bytes (2%) of program storage space. Maximum is 32256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
/Users/christyyau/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino17/bin/avrdude -C/Users/christyyau/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino17/etc/avrdude.conf -v -patmega328p -carduino -P/dev/cu.usbmodem11201 -b115200 -D -Uflash:w:/var/folders/b3/y_g3drns0rn7hml6sn82s3jr0000gn/T/arduino_build_400066/sketch_sep09a.ino.hex:i

avrdude: Version 6.3-20190619
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch

     System wide configuration file is "/Users/christyyau/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino17/etc/avrdude.conf"
     User configuration file is "/Users/christyyau/.avrduderc"
     User configuration file does not exist or is not a regular file, skipping

An error occurred while uploading the sketch

     Using Port                    : /dev/cu.usbmodem11201
     Using Programmer              : arduino
     Overriding Baud Rate          : 115200

avrdude: ser_open(): can't open device "/dev/cu.usbmodem11201": No such file or directory

avrdude done. Thank you.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

2

I have no idea about Macs.

Does /dev/cu.usbmodem11201 disappear from the IDE's port options when you disconnect the board?

The Mac should have tools that can show you what is going on under the hood. Under Linux, it would be dmesg and lsusb; do they exist on a Max?