If the exported DNG Works fine in Lightroom and Photoshop.It must be something wrong with the other Product you are using?
Have you checked if this Product can process DNG images?
Here is a discussion on the similar topic Help with Deep Sky Stacker using Sony 5n .ARW files: Astrophotography Talk Forum Forum: Digital Photography Review
My guess is that the converted DNG still looks enough like an ARW file internally that Deep Sky Stacker can't interpret it properly. Your best course of action would be to convert to a TIFF or some other non-raw format. Here's the appropriate line from their documentation:
Supported bitmaps formats : 8, 16 and 32 bit colour and monochrome TIFF files, 8, 16, 32 and 64 bit colour and monochrome FITS files, JPEG, BMP, PNG
with tiff i already tried to use in DSS... The problem: if i stack many pics to one, i cant see the darker objects like a nebula. not even the orion-nebula. And this is very easy to see...
it works with the Adobe DNG Converter 9.3!!