Avr G++ error - Bad CPU type in executable

Hi everyone,
So I know that this has been asked in another thread (https://forum.arduino.cc/index.php?topic=620175.0)
but after trying all of the possible fixes suggested, I am receiving the error

"fork/exec /Users/mitchellostler/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-g++: bad CPU type in executable
Error compiling for board Arduino/Genuino Uno."

This seems to be a compatibility issue, but I have updated to the latest avr tool chain from here, downloaded a more recent build from the github, and this has not solved it

Thanks

Which board do you have selected from the Arduino IDE's Tools > Board menu?

Which version of the Arduino IDE are you using?