Step 1: Move Away From the Edge
RetinaEngrave won’t "print" parts that are outside the edge of your page, but it also won’t print items that are too close to the edge. Try moving your graphics at least one inch away from the edges. You can move things on and off the page to print multiple parts.
Step 2: Set Your Stroke Opacity to 100%
RetinaEngrave ignores objects whose stroke opacity is at less than 100%. Select all of your objects, pull up the Stroke Paint panel, and set this slider to 100%. You may need to set the slider to a lower number, then move it back up to max.
Step 3: Combine Paths of the Same Color
If your design contains many objects, RetinaEngrave may not see all of them. This commonly happens with text. Select several or all of the objects that have the same stroke color and Combine Paths. (You can undo this later with the Break Apart function.)
AvramP made it!