Unable to update or synch with Garmin Express.

I assume your 935 is plugged via usb cable to the computer that is running Garmin Express?

Using Garmin Connect on Your Computer

KDREWTOFU said:

The reason I cannot update my software is that Garmin Express does not recognize my watch, a Forerunner 935.

As seilogramp wrote, make sure and check on your Mac, that the watch is connected by the USB cable, and that it is recognized by the Mac on the USB port. If it is not the case, try another USB port, or preferably another computer (family member, friend, work,...). Alternatively, try updating the watch through Garmin Connect Mobile on a phone.

KDREWTOFU said:

Also, when I run and the GPS kicks in, I press the start button and nothing happens.

You need to select the Running Activity, then wait for the GPS signal (check-sign in the GPS status), and then pressing the start button again. In that moment nothing extraordinary happens, just the timer (and other fields) start counting up. If you already started the Activity after selecting it, without waiting for GPS, the timer starts counting immediately, just the distance won't be corrent until the GPS status is OK. After it "kicks in" as
you write, nothing new happens, just the track starts being recorded correctly. If you are not exactly sure how to use the watch, there are many videos on Youtube demonstrating it in details.