Raised Letter Signs

I’m having trouble with stacked lettering. I stack the text, make a copy of the top text and move it off of the design. I then do the Boolean to combine them, but the centers of the A and D disappear. Can’t figure out what im doing wrong.

Will did a fairly decent write up of the process here: Could use some guidance on creating a carve

Hopefully going through that walkthrough helps. If not, you could post the file?