My problem was that I previously installed the FTDI drivers on my MAC even though I was working with an Arduino Mega (Which does not need those drivers) . Apparently the arduino program was using those drivers to communicate with my Mega that is why in Tools-Port I had tty-USBSerialxxx. I uninstalled those drivers and I got tty.usbmodem1411. My arduino MEGA ran perfectly fine. I hope this helps 