I have a D-VR17 DVD/VCR recorder unit which I cannot make record vcr to dvd. I have tried putting in the video then the disc and pressing the dubbing button. I get a white circle with a line through it like a no entry sign on the TV and when I persist on the TV screen it says "you cannot record on this disc". I have tried three discs from various packs but no luck. Can you help please ? My model does not have the KB at the end. Thank you.