Uploading code to Mega 2560 is stuck
I would suggest to download the Arduino app (https://www.arduino.cc/en/Main/Software).

Download both the latest version and an a legacy build (https://www.arduino.cc/en/Main/OldSoftwareReleases#00xx). Within the DMG for the legacy you'll need to install the FTDI drivers to allow Arduino app to see the Arduino in ports.