I FOUND A FIX… All initial failures were with the default Arduino IDE “Tool” settings for the Sparkfun ESP32 IoT RedBoard.
I played with the flash frequency and upload speeds and settled on these selections as working solutions. Your final choice may depend upon your computer and router performance.
DEFAULT SETTINGS - ALWAYS FAILS TO UPLOAD
- Flash Frequency: “80 MHz”
- Upload Speed: “921600”
INITIAL FIX - UPLOADED!
- Flash Frequency: “40 MHz”
- Upload Speed: “115200”
SUBSEQUENT FIX - WORKS EVERYTIME
- Flash Frequency: “80 MHz”
- Upload Speed: “460800”
FINAL FIX “SAFE SOLVE”
- Flash Frequency: “80 MHz”
- Upload Speed: “115200”
I USED THE APPLE BUILT-IN STANDARD CH340 USB DRIVER THAT CAME PRE-INSTALLED. Do not install any third party .kext files! These are for the old macOS 10.x that have been obsolete for many years. Apple no longer uses .kext files, they have been replaced with the more secure .dext drivers.