1. Make sure your imported artwork is the same size as your screen area. Personally I use 1080 X 1920. (I think that's the proportion)
2. In your artwork, you may have a tiny little thing somewhere outside the drawing area. To check this I go to the original artwork- I shrink it and then "select all" If there is a little something it should show up. Erase it and you're all set.
I've been where you have many times-it's annoying. Good luck