Fixed it!
Used the wrong midi settings in Ableton's Preferences.
While using the 'external instrument' container for the Microbrute I have the following midi port settings:
Input section: everything is switched off
Output section:
- Turn the 'Track' and 'Sync' option ON for you audio interface
- Turn the 'Track' and 'Sync' option ON for you MicroBrute
- Turn the 'Track' and 'Sync' option ON for you MicroBrute (port 2) (if you have this option)
Tip: Ableton now has a max for life midi device that helps you midi control MB's modulation options etc from live and Push