I'm going to go out on a limb and say that it almost certainly is a focus issue. If you can focus it with the eyepiece, you will almost always need to move the focuser inwards to find the position it will focus with a camera. This is the problem with most newts - they don't allow enough inwards travel to get focus with a camera. I had to move the mirror in mine up the tube by fitting longer collimation bolts and stiffer collimation springs - but there are other solutions such as a low profile focuser, or more drastically cutting the tube to get the mirror closer to the camera.
The best thing to do is try to focus it during the day on something suitably distant - the further the better (just not the sun!
) so you can get a feel for where the focal point is. Then make a mark on the focuser drawtube so that you can get it somewhere close when you go out in the dark
Good luck
Adam