- If you are getting errors compiling for a printer with the 2560 board in it go to Tools > Boards > Board Manager. Look for ATmega2560 & revert to 1.6.21. Some users reported issues on Mac OS X with the latest 2560 board library.
- If you are having issues with uploading and/or connecting to your printer board over the USB port try updating the drivers. They are included in the Unified Firmware download and available separately here: CH340 Drivers & FT232 Drivers
Download the latest firmware pack that contains the latest Mac Arduino IDE and the TH3D Arduino Library Files from here: TH3D Unified Firmware Package
Please note the screenshots mention arduino-1.8.7. As the version is updated please open whatever the latest arduino-XXX-macosx.zip file is in the package downloaded above.