[Steve Marcotte]

My Mbox Pro 3 is now working on High Sierra 10.13.6.

I just installed 10.13.6 yesterday and had the same problem of the Mbox Pro 3 not showing up as device. I searched the forums for answers and found a lot of people have the same problem. I found a reply from Eggbox in the thread Mbox Pro 3 not recognized on Sierra and used it as a guide although it was for Sierra rather than High Sierra.

I just got it working by the following. Note that you need to reboot after each step.

1. Download the 1.3.5 driver. Use uninstall to get rid of the 1.3.5 driver
2. Download and Install the INCORRECT Mbox (Not Pro) driver 1.2.13
3. Uninstall 1.2.13
4. Install 1.3.5 driver again

My Mbox Pro 3 showed up as a device and now works (so far) on High Sierra 10.13.6. It seemed to take forever to start up Pro Tools (2018.7) the first time but eventually it came up and it's working.

I hope this will work for other folks!