Can't get adb on Macbook to see Pixel C

I'm trying to connect my 2014 Macbook pro to a Pixel C tablet. The tablet has developer settings enabled, usb debugging enabled and unknown sources enabled. 'adb devices' shows nothing and there is no debug icon shown on the tablet.

I'm using a usb 3 type C connector that works Perfectly from my Macbook to my Nexus 5x

I've tried resetting the PRAM/NVRAM and the SMC to no avail.

The strangest thing is that we have 3 developers here with 2 ports per macbook. It does work on ONLY 1 port on one macbook, a 2015. We have a second exact same macbook bought on the same day that this tablet doesn't work on either.

Since it works on 1 port on one macbook, we know that the tablet is configured correctly for debugging. But why can't we connect it to the second port on the same machine or to another macbook??

We've never had any issues connecting any other Android device to any of these macbooks before.

Updates:

1. Got a different usb C cable and still have same issue.


2. Default USB Configuration (from Dev Options) is MTP, tried other USB config PTP and didn't help


3. After testing again on the 1 port that it worked in the past, trying 'adb devices' shows the Pixel C about 3 out of 5 times (in the span of 10 seconds). Trying to deploy to the device fails every time, presumably due to the flakey connection...