After updating the Microbrute firmware, many people have had the sequencer stop working.
I just got mine working today.
I wanted to change the settings so that the sequencer would play without having to hold down a key.
I changed the setting the other day, and got no sounds.
Today, I put the actual sequencer switch into the "Play" position while changing the MIDI Control Centre settings, and it just started playing.
Remember to connect the speakers or amplifier.
Arturia page:
https://www.arturia.com/faq/microbrute/my-microbrute-sequencer-doesn-t-work-anymore-why