MBox Pro 3 + 2017 iMac + Thunderbolt->Firewire adapters + latest drivers = success

[drooster]

I upgraded my computer to a new late-2017 27" iMac and spent a ridiculous amount of time trying to get my MBox Pro 3 to work on it, and was actually successful, so thought I would share what I did since I haven't seen any other threads on this:

1. Bought a new 2017 iMac that came with High Sierra (10.13.2) installed and no firewire ports
2. Used the following adapters to connect to the MBox Pro: iMac->Thunderbolt 3 to Thunderbolt 2 adapter->Thunderbolt 2 to Firewire 800 adapter->Firewire 800 to Firewire 400 adapter->Firewire 400 cable to MBox pro (side note: I still can't believe this worked)
3. Installed latest MBox Pro 3 drivers (1.3.5)

At this point nothing worked, the MBox control panel said "Hardware not connected", etc. So here's what I did:

4. Ran System Profiler (Apple Menu->About this Mac->System Report)
5. Looked under "Thunderbolt" and verified that the Thunderbolt 2 to Firewire 800 adapter was present
6. Looked under "Firewire" and verified that the MBox Pro is present. When I first looked under "Firewire", it showed "unknown device", so I reinstalled the driver and power cycled the MBox Pro 3, and then it showed up as an MBox Pro.

At this point the device showed up in System Profiler but the MBox control panel and Pro Tools still couldn't recognize it, until:

7. Opened Control Panel->Security and Privacy, saw the message "System software from developer 'Digidesign' was blocked from loading", and clicked on the "Allow" button.

After all of this, everything worked. Apparently there is a new "feature" in Mac OS 10.13.2 that requires a user's approval before installing 3rd party drivers, and for whatever reason the MBox Pro driver installer did not prompt me for for approval. Hope this helps someone.