Not a Mac person, but when you say can't get Teensy to run, you are talking about the Teensty firmware loader app for the Mac, right?
On the Teensy loader page for Mac:https://www.pjrc.com/teensy/loader_mac.html it says you are running a "disk image". So you downloaded the teensy.dmg. When you double click it, what happens?
Do you get an error message? What is it? Can you post an image of what you see, then maybe someone with Mac experience can chime in if I can't figure it out.
On the Teensy loader page for Mac:https://www.pjrc.com/teensy/loader_mac.html it says you are running a "disk image". So you downloaded the teensy.dmg. When you double click it, what happens?
Do you get an error message? What is it? Can you post an image of what you see, then maybe someone with Mac experience can chime in if I can't figure it out.