Works for me on both mac and windows.
On mac it's command + shift + m.
Software developer, Sound Engineer,
Control Your show with ”Enter” - multiple Resolume servers at once - SMPTE/MTC column launch
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Ok I found the problem.
I could see, after Zoltans post, that it worked on my mac either.
In my case the Radeon driver blocked the hotkey for mute/unmute microphone.