What am I doing wrong pulling my hair out!

I have been working on this model and was very careful about start and end points. I ran the solid program and got this help me understand what to do please.

Very hard to tell unless you attach the model for us to look at.

How do I do that

Use the Download option found under the top left hamburger menu to download the .skp to your computer then drag and drop it into a reply window.

Here’s a video on how to do that in SketchUp Web. It might be similar in SketchUp Shop, but I’m not sure.

Hope this helps!