Ok, I could narrow down the problem…
Was checking out the new Quartz system earlier today (which is awesome btw) and all of a sudden the reverb was working…
The only difference was, that i had my stereo system connected and not the surround setup…
Switched back to my 5.1 setup—> reverb gone
Back to 2Channel Stereo: reverb working again…
up to 4.25 reverb was working with my surround-setup as well…