Sudden failure to upload

I have an Arduino Mega which has been working reliably. Yesterday it suddenly stopped allowing me to upload sketches. The board appears correctly under the Port option of the Tools tab. I am using the programmer 'AVR ISP' as I did when the board worked. I receive the following error message when trying to upload.

Arduino: 1.8.13 (Mac OS X), Board: "Arduino Mega or Mega 2560, ATmega2560 (Mega 2560)"

Sketch uses 1536 bytes (0%) of program storage space. Maximum is 253952 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 8183 bytes for local variables. Maximum is 8192 bytes.
/private/var/folders/0f/qr05v6sn58x_hq42l_3rl3440000gn/T/AppTranslocation/326A3C8C-1D9F-47E7-B31E-11CB1BBE0220/d/Arduino.app/Contents/Java/hardware/tools/avr/bin/avrdude -C/private/var/folders/0f/qr05v6sn58x_hq42l_3rl3440000gn/T/AppTranslocation/326A3C8C-1D9F-47E7-B31E-11CB1BBE0220/d/Arduino.app/Contents/Java/hardware/tools/avr/etc/avrdude.conf -v -patmega2560 -cwiring -P/dev/cu.usbmodem14101 -b115200 -D -Uflash:w:/var/folders/0f/qr05v6sn58x_hq42l_3rl3440000gn/T/arduino_build_989642/Blink.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 "/private/var/folders/0f/qr05v6sn58x_hq42l_3rl3440000gn/T/AppTranslocation/326A3C8C-1D9F-47E7-B31E-11CB1BBE0220/d/Arduino.app/Contents/Java/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/Users/peterburton/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/cu.usbmodem14101
         Using Programmer              : wiring
         Overriding Baud Rate          : 115200
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

avrdude done.  Thank you.

An error occurred while uploading the sketch


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

"I am using the programmer 'AVR ISP' as I did when the board worked."
That only comes into play with Upload Using Programmer and having a Programmer connected to the ICSP header.

Does the Loopback test still work? Connect Reset to Gnd, connect D0 to D1, open Serial Monitor and type stuff in, it should get echoed back.