After emailing Doepfer support and talking with the guys over at Analogue Haven I decided to send the keyboard back to get it looked at. And it turns out that it *was* defective and not just my imagination. Analogue Haven were really cool about it and sent me another one. This time, all I did was plug the DE into my keyboard controller and everything worked.

I might try and find out the exact cause of the issue some time soon but Doepfer support did mention that "if the ADSR responds (the ADSR light was on and responding) the Dark Energy reacts obviously to incoming note messages and it's not a Midi learn issue but something else (probably a pitch CV issue)."
thanks again everyone for your help, I do appreciate. If it weren't for everybody's input and knowledge I would of been totally lost *and* I could of easily continued on buying different keyboards ( (like an idiot), thinking that was the issue. Or even worse try and open it up and and try and fix it!
jim