Thanks for reaching out and sorry to hear that you're having trouble in desktop preview in XD. Basically black screen appears in preview window becuase of the different size artboards and In the screenshot which you have shared with us, I see a white line in the preview window might be because of the viewport height so make sure your viewport height value is equal to height the artboard . Also I'd request few more details to analyse your Issue thoroughly:
The version of XD.
The version of Mac or Win which you are using.
If it is happening with a specific file or multiple files, will it be possible for you to share the file with us?
What is the size of the artboard you are using.
what is the value of Viewport height on the artboard you are using to preview.
Is it possible to share a video of your workflow which you are working on so it will be useful to clearly reproduce the issue from our end. so please share the above mentioned details.