Web Editor works fine -- Stand Alone Arduino IDE is a total Fail

This makes no sense.

I've got two brand new boards, one an authentic Arduino Due and the other a Elegoo Mega2560.

Laptop = Macbook Pro, running macOS High Sierra, version 10.13.5

I've tried both boards with the IDE. Total fail. I keep getting "programmer is not responding" errors.

I tried both the Arduino 1.8.5 version as well as the Beta version 1.9.0-beta . Total fail in all combinations.

I tried the Web Editor of the Arduino software. Works great, both boards, way easy.

The problem is I have to do some programming on a job site in a remote location where I know there is no internet access.

This baffles logic. Obviously its not a board, cable or interface issue. What content does the browser web editor provide that is missing from the stand alone IDE program? Anybody been here before?

Many thanks.

Please enable verbose upload (turn off verbose compile) in preferences, attempt upload, and post the output. Whenever you ask a technical question anywhere, you should always post the full text of any and all error messages.

I hear more people saying that they can't make the web editor work than the other way around....

Per request, here is the upload response for the program "Blink"...

Arduino: 1.8.5 (Mac OS X), Board: "Arduino/Genuino Uno"

Sketch uses 928 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/__myUser
Name__/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/bin/avrdude -C/Users/__myUserName__/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/etc/avrdude.conf -v -patmega328p -carduino -P/dev/cu.usbmodem1451 -b115200 -D -Uflash:w:/var/folders/yc/3v6d5mhj1lnc17ktfl9l43zh0000gn/T/arduino_build_572593/Blink.ino.hex:i 

avrdude: Version 6.3, compiled on Jan 17 2017 at 12:01:35
        Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
        Copyright (c) 2007-2014 Joerg Wunsch

        System wide configuration file is "/Users/__myUserName__/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino9/etc/avrdude.conf"
        User configuration file is "/Users/__myUserName__/.avrduderc"
        User configuration file does not exist or is not a regular file, skipping

        Using Port                    : /dev/cu.usbmodem1451
        Using Programmer              : arduino
        Overriding Baud Rate          : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

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

Works just fine using the browser version "Arduino Create". I just checked it again.

Finally got this working.

I had to add the Atmel SAMD Core via Board Manager, then enabled the Board = Arduino Due (Programming Port) . Reference here...

Not sure why this didn't work originally, while the browser version worked smoothly without any extra installs.

Info posted here for anybody else who gets stuck at the same issue...