Mainstage 3: Wait for Audio Units when opening Halion

Hi everyone,

for a few days, when I'm trying to open the Halion-Plugin in mainstage, I get a little window which says "waiting for audio units". After that, nothing happens and mainstage cannot longer be used, unless I quit it "hard".

Does anybody know this issue and has probably an idea, what to do?

I can add a screenshot.

Thanks for your support!

Patrick