Denon AVR 1707 Subwoofer problem

[CiTor]

Hey guys!
I just got a new speaker system from Teufel (Concept M) with an active Subwoofer. I also got a Denon AVR 1707 and hooked up the 5.1-version of the speaker-system to my receiver. I've hooked up my bass with a cinch cable to the PRE-Out just like it says in both of the manuals but it just won't work! Just a couple of hours ago the sub at least played a test tone but now even that's gone. If I touch the sub-cable the sub responses as if it is still working properly but I just can't get it to produce any real sound from my receiver. I think that all the settings are set correctly (the sub is turned on and is set to normal) but Im probably wrong

does anyone have an Idea what else I could try to do, to get this thing working? Is there some kind of reset-function on the receiver to get a clean-start? That way I could at least check if the PRE-out on the receiver is still working...

I'd be really glad If someone could give me a slight bit of advice! Thanks in advance..