hey
@Darryn, you might want to check out this thread over on Apple.
https://www.apple.com/shop/question...to-an-old-firewire-400-port/QU9FDKH2979JHJ7CK
There's lots of useful stuff there about the exact daisy chain you're using. And I also found this reply:
"I got Focusrite Saffire Pro 40 working with OWC Thunderbolt 3 Dock using a Firewire 400 to Firewire 800 adapter, connected to a 2017 MacBook Pro running Mac OS 10.13.1. If you see a situation where the Mac system report shows the Thunderbolt 3 device, and the Saffire Pro 40 Firewire device, but not the audio device, then this is likely a preference problem. Try removing all your audio preferences, and rebooting. This worked for me. Remove these files and reboot:
/Macintosh HD/Library/Preferences/Audio
* com.apple.audio.DeviceSettings.plist
* com.apple.audio.SystemSettings.plist
~/Library/Preferences
* com.apple.audio.AudioMIDISetup.plist
After doing this, all my Firewire audio devices are now showing up on my new MacBook Pro connected through Thunderbolt 3."
Could you try this and see if it works? Looks like the exact problem you're having. I have to say they are using a dock to convert from firewire to Thunderbolt.
And like
@Peter Batah says: google is your friend.